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I I How diesel-electric locos killed off steam $3.50 DECEMBER 1988 NZ S4.95 ~Ng High Performance In Your Shirt Pocket! 3 l /2 digit LCD Display Ranes Max Res Accurac Vdc Vac Ade 100µV 1mV 100µA 10mA 100µA 10mA 0.Hl 200mV-1kV 2V-750V 200mA 10A Aac 200mA 10A Ohms 200O-2Mf.l 0.5% + 1dig 0.75%+5dig 0.75%+ 1dig 1.5%+5dig 1%+5dig 2%+7dig 0. 75%+ 1dig Display also has Low Battery & Over-Range Indication Built In Diode Check, Lo-Power Ohms & Continuity Test Beeper Memory Function for Relative Readings (DM6235 & DM6335) Autoranging Manual Ranging Over-Ride (DM6235 & DM6335) One Year Warrant Hold Reading Function (DM6335) 10A Range Automatic Current Limiting Overload Protected to 1000Vdc/750Vac $88.80 $99.60 Look At The Low Pricesl DM6135 Autoranging 3 1/2 digit 10A ac/dc DM6235 As above with Memory function and Range Hold Prices include 9V Battery and High Quality Silicon Rubber Test Leads with Screw-On Alligator Clips DM6335 As above with Data Hold l0MQ Input Impedance Gotta Gatta GoldStar Dealer enquiries welcome. Call (02)736 2243 Recommended prices only including Sales Tax $118 • 80 You 've Gotta Getts Goldstar from : M.,L John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355 N.S.YI', Ames Agency 699 4524 • J Blackwood & Sons• George Brown 519 5855 Newcastle 69 6399 • Auto-Catt Industries 526 2222 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ebson 707 211 1 • Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Pty Ltd 698 4776 • Petro-Ject 569 9655 • David Reid 267 1385 • Digitel 709 6511 • Geoff Wood 427 1676 N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 QUEENSLAND Auslec (07) 8541661 • G. Brown Group (07) 252 3876 • Petro -Ject (075) 91 4199 • St Lucia Electronics 52 7466 • Cliff Electronics 341 4655 • L.E.Boughen 369 1277 • The Electronics Shop (075) 32 3632 • Thompson Instruments (Cairns) (070)51 2404 • Nortek (Townsville)(077) 79 8600 S.AUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688 • J Blackwood & Sons 46 0391 • Petro-Ject 363 1353 TASMANIA George Harvey (003) 31 6533 (002) 34 2233 VICTORIA Radio Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 4301 • A.W.M. Electrical Wholesalers• Petro-Ject 419 9377 • J Blackwood & Sons 542 4321 • Factory Controls (052) 78 822 • Mektronics Co 690 4593 • Truscott Electronics 723 3094 W AUSTRALIA Atkins Carlyle 481 1233 • Dobbie Instruments 276 8888 • Protronics 362 1044 DECEMBER 1 988 THIS IS THE VIEW inside our rugged new 120W public address amplifier. This month, we describe the circuit and show you how to assemble the PCBs. See page 26 FEATURES 4 Electronics & Holden's V6 Engine by Leo Simpson The end of the distributor 18 Harman Kardon P~665Vxi Amplifier by Leo Simpson A high power, high current design 42 Kit Clinic & the 1 00W Power Module by John Clarke How we solved one reader's problems 76 The Evolution of Electric Railways by Bryan Maher Pt.14: Why diesel-electrics killed off steam PROJECTS TO BUILD WANT REALISTIC SOUND effects for your model railroad layout? Our new diesel sound generator has all the desired features. Construction starts on page 50 26 120 Watt Public Address Amplifier by Bob Flynn The microphone preamplifier and mixer stages 34 Simple Car Antenna Adaptor by John Clarke Use your rear window demister as an antenna 50 Build a Diesel Sound Generator by Greg Swain The sound follows the locomotive SPECIAL COLUMNS 14 Vintage Radio by John Hill Restoring the dial mechanism 44 The Way I See It by Neville Williams Would you please pass the salt? I need a few grains 62 Serviceman's Log by the original TV serviceman The customer has no idea 70 Amateur Radio by Garry Craft Simple SSB adaptor for shortwave receivers OUR INTREPID SERVICEMAN this month battled both the set and the customer. His frustrations with both begin on page 62 DEPARTMENTS 2 Publisher's Letter 3 Mailbag 59 Circuit Notebook 83 Subscription Page 84 Product Showcase 90 Ask Silicon Chip 92 Back Issues 96 Market Centre 96 Notes & Errata FED UP WITH REPLACING you car radio antenna? This gadget will let you use your rear window demister instead. We show you how on page 68 DECEMBER 1988 1 SILICON CHIP Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill David Whitby Photography Bob Donaldson Editorial Advisory Panel Philip Watson, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Waterloo, NSW 2017. Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rate: currently $42 per year (12 issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. ISSN 1030-2662 • Recommended and maximum Australian price only. 2 SILICON CHIP PUBLISHER'S LE'1·1'ER End of volume one; start of volume 2 Every month the production of SILICON CHIP is a matter of following a tight schedule as all the various articles are prepared, written, typeset and laid out. It's a lot of work as you might imagine but most of it is largely routine; it has to be that way to keep to the schedule. Some tasks are not routine though, especially if they have not been done before. One such task this month was the preparation of the index for our first volume which spans 14 months, from November 1987 to this month, December 1987. Inevitably, the preparation of an index must cause a review of what has been done in the past and when we look back it is with a certain amount of satisfaction. Our · first volume contains over 1000 editorial pages, with an average of around 600 words per page. That adds up to over 600,000 words and millions of keystrokes to prepare the editorial material. There are hundreds of diagrams, photographs and cartoons and, of course, the core articles which are our constructional projects. All told, there were over 60 constructional projects, with some running over more than one issue. · The numbers merely emphasise the large amount of work which has gone into SILICON CHIP. All this work would be for nought though, if it was not for the large amount of positive feedback we have received from you, the readers, in literally thousands of letters. These have been very encouraging. In the first few months after we launched SILICON CHIP a number of readers expressed doubts as to whether we could maintain the high initial standard. Now, there seems to be general agreement among readers that not only have we maintained the standard, we have improved it. Thank you to all those who have written in with constructive criticism. We are striving to do even better. We have some great projects planned for the new year. Some of these are already finished and are merely waiting for the day when the semiconductor companies can supply production ICs. In fact, that is one of the traps in using new semiconductors in our constructional projects. Sometimes the devices are so new that the semiconductor manufacturers have yet to put them into full production. Innovation sometimes has its price. When all is said and done though, we look back upon our first year as having been an enjoyable challenge. We look forward to our next year with great anticipation. Leo Simpson MAILBAG Noisy motors in model locos After reading your article in the April issue of SILICON CHIP on the W alkaround Throttle for Model Railroads, I purchased a kit from Jaycar. Although I know little about electronics I found it very ~asy to put together due to your excellent diagrams and explanations. After overcoming a minor problem, it worked and did everything it was supposed to except I had motor growl. Then, in the June issue, I read where a reader from WA asked how to change the pulse frequency. I followed your suggestions but the problem is still there. I've had my controller checked out by an electronics technician and he confirms that I have everything where it should be, so I'm hoping you could throw some light on how to overcome this growl. My layout has taken a back seat for a few months and now I would like to blow the dust off and give it another go. Thank you for an interesting magazine. Chris Simons South Melbourne, Vic Comment: Motor 'growl" is a characteristic of pulse power control, so your unit is working as intended. For further details, see our answer to another reader in the Ask Silicon Chip pages. Optical tachometer danger Your May 1988 magazine has an optical tachometer project to build which, I have no doubt, is excellent in · itself. As a state qualified instructor in the sport of flying model aeroplanes by radio control, I would point out to you the danger of tuning an engine from in front of the propeller. This is lesson 1 (often repeated) until a beginner learns to start an engine at low throttle and move behind the propeller before opening up or removing the glowplug connection or adjusting the mixture. Your photographs clearly show someone at risk if a propeller breaks. With a tip speed in the vicinity of 150 to 200 metres per second, you don't have time to duck. Also if the helper loses grip on a vibrating, generally slippery surface and the aircraft surges forward, the prop would make short work of the tacho and possibly the hand holding it. (A modern 10cc standard engine develops 1.8HP, a competition engine 3HP or more). For the competition flyer, ground running rpm is not the only indication of correct tune. Perhaps your contributors could come up with an adaptation using a cheap microphone insert to acoustically measure rpm. With the advent of ducted fans there is no access to a rotating part. This could also be used to determine rpm in flight, at a point perpendicular to the line, as this is of more interest to a competition flyer than ground rpm. A switch could be added to select either 4-stroke or 2-stroke. Stephen Vickers Denistone, NSW Comment: Yes, there is some risk in the procedure we show but no more risk than occurs during starting or throttle adjustment. Smell of an oily battery All of us who fiddle with and think about small battery powered electronic devices are constantly trying to squeeze the desired functionality into the minimum possible volume. During my experience with pagers a couple of years ago, I was continually amazed at the performance the Japanese could get out of a single AA-size penlite battery. I think a lot of professional and amateur readers would be interested in: (1). A review piece along the lines of the miles/gallon marathon which perhaps looked at highly efficient battery-powered DC-DC power converters. I am thinking specifically of pagers, watches, digital thermometers, digital display vernier calipers, and digital humidity and pH meters etc. (2). A construction project which offered a design for a single AAA or AA battery source which could be efficiently stepped up to 5V, 6V, 9V or 12V DC. This could cover a lot of home and mobile electronics applications (both analog and digital). SILICON CHIP, PO Box 139, Collaroy Beach 2097. Maybe it could be run as a competition to see how far a little "mouse" or "carriage" could run on a single fresh battery on a flat surface. Ian Rowatt Koolewong, NSW Wants TV reception on FM antenna I have just purchased the October issue of SILICON CHIP and it is yet another fabulous issue. I particularly liked the 5-element FM antenna article by Leo Simpson and Bob Flynn. I would be interested to know if the antenna could be used to pull in a good signal for ABC Channel 2. I have little knowledge of technical radio, however I do recall ABC TV being on (or near) the FM waveband and I wonder if the antenna would be suitable for this purpose. Samuel Venning Port Melbourne, Vic Comment: The FM antenna was not designed for TV reception although it should perform well on channels 3 and 4. For channel 2 reception you would probably get better reception from a 3-element Yagi cut specifically for the job. Project suggestion As a very keen fisherman there is a project I would like you to consider one which would not only be appreciated by fishermen but by all people who "go down to the sea in ships". I am referring to a "tide clock". The tides on the east coast are approximately 24 hours & 50 minutes from one tide (high or low) to the corresponding tide the next day (eg, from high to low to high to low to high). There are a number of commercial units available but cost from $110.00 to $185.00. Most use a quartz movement that has been adjusted to give one complete rotation of a single hand every 12 hours and 25 minutes. The more elaborate types show both actual time and tide time but I feel a single hand showing the tide only would be sufficient. I hope you can develop such a project. J. Harvey Port Macquarie, NSW DECEMBER 1988 3 By LEO SIMPSON Released on to the Australian market only a few months ago, the Holden VN Commodore represents another stage in the integration of electronics into automobiles. It is a large car with a big motor but electronics enables it to give a high level of performance with improved fuel economy. It must come as a surprise to many people to learn that the new VN Commodore has the biggest six cylinder motor ever fitted into a Holden. It is a whopping 3.8 litre V6. As you might expect, it offers sparkling performance but it is lighter and more compact than previous Commodore engines and 4 SILICON CHIP gives better fuel economy. The reason it does give better fuel economy is because of electronics, in the engine management system and in the ignition system. General Motors has certainly had its ups and downs in recent years in the Australian market. Some years ago, rather than spend the money to develop an improved engine, the company committed itself to using the Nissan 3-litre fuel injected engine. This was featured in the VL Commodore. Unfortunately, the relative movements of the Australian and Japanese currencies then made that engine far too expensive. Holden's new 3.8 litre V6 motor does not have a distributor or conventional ignition coil. Instead, it uses Direct Fire Ignition, a system with no moving parts. Three double-ended coils, mounted on a module at the front of the engine, fire the six plugs directly. General Motors then had to find a cheaper engine but one with at least equivalent performance to the Nissan unit. Fortunately, they were able to use one employed in the compact American Buick. This 3.8 litre V6 unit had originally been cut down from a larger VB and in its first version had been a rough running engine. This was because the angle between the cylinder banks was 90° whereas 60° is the ideal angle for a V6. This rough running was one of the reasons that General Motors had not originally adopted it for Australia. Fortunately, a later model of the engine incorporated a balance shaft, similar to that first used on the Mitsubishi Sigma 4-cylinder engine, and this led to very smooth running. The engine is now being assembled in Australia, from American parts, although the inlet and exhaust manifolds are made here. Engine installation The engine bay of the new Holden Commodore is notably clean and uncluttered. This makes a pleasant change from the "chock a block" installations on most modern cars with their complex plumbing, multiple belt drives for all the accessories and a huge air cleaner hiding it all. Since the V6 engine is so short, it sits well back in the engine bay, which incidentally leads to improv- DECEM BER 1988 5 -- +12v------. CONTROL CIRCUIT CAPACITOR POINTS+ .,. Fig.1: a conventional transistor switched ignition system uses one coil and a distributor. The plugs are negatively polarised to lower the required firing voltage. The arrows show electron current flow. ed weight distribution in the car. Apart from its more compact size though, there are several reasons why the V6 looks less complicated and cluttered than engines in other modern cars. First, it uses direct fuel injection into each inlet port so instead of a complicated multibarrel carburettor there is a simple throttle body (containing a large butterfly valve linked to the accelerator pedal). The throttle body is linked via a large diameter duct to the aircleaner which sits on the righthand side of the engine bay. Second, it uses a long "serpentine" belt to drive the accessories rather than the multiple belts used in other cars. The one long belt drives the water pump, alternator, power steering pump and airconditioning compressor. The radiator fan is electrically driven and controlled by the engine A Hall Effect sensor and magnet system generates timing pulses from these toothed wheels mounted behind the harmonic balancer. 6 SILICON CHIP Fig.2: this diagram shows one of the three coils in Holden's Direct Fire Ignition. Each coil simultaneously fires two plugs, one with positive polarisation, one with negative polarisation. management system which we'll talk about later. Third and perhaps of most interest to readers of SILICON CHIP, the usual ignition coil and distributor is not present on the V6 engine. Instead, it uses a new computer controlled ignition system with no moving parts at all. General Motors call it "Direct Fire Ignition" (DFI} and it is made by their AC Delco division. Direct Fire Ignition Commodores have had solid state ignition systems since 1980 while more recent models such as the VK and VL had electronic spark timing (EST) via sensors mounted on the flywheel. However, they still employed a more or less conventional ignition coil and HT distributor. In the new model with V6 engine, all that has gone out the window and is replaced by a system which is housed in one module adjacent to the alternator. All six spark plug leads plug into this module. Its workings are quite different to conventional transistor switched ignition systems. Inside the module are three double-ended ignition coils, each driving two spark plugs. Each pair of spark plugs is fired simultaneously by its associated coil which means that while one plug fires at just before TDC (top dead centre) for the power stroke another plug fires at just before TDC for the exhaust stroke. This brings up a number of in- teresting points. In a conventional ignition system, as shown in Fig.1, the spark plug is polarised so that its centre electrode is negative with respect to the outer core. In this way, the voltage needed to fire it is reduced by 30 % compared to the alternative connection whereby the centre electrode is positive. Spark plugs in series This situation cannot be obtained in the Commodore V6 though, because of the double-ended ignition coils. The circuit configuration is as shown in Fig.2. Effectively, the coil secondary is connected in series with the two spark plugs. One plug is fired with the "correct" negative polarisation as in a conventional system while the other plug has positive polarisation of the centre electrode. In practice, this makes no difference to the reliability of the ignition since the coil has more than enough secondary voltage to fire both spark plugs. Open circuit voltage is more than 40,000 volts. The only real consequence of the differing polarisation for each pair of spark plugs is that after a long period of use, those plugs with negative polarisation will have erosion of the centre electrode while those with positive polarisation will have erosion of the outer electrode. Even this is of no importance since General Motors recommend that the spark plugs be replaced after 15,000 kilometres. After this period of use they will have negligible wear but the additives in lead vance or centrifugal advance system. All the engine timing information comes from the main electronic control module (ECM) which performs all the engine management functions. However, the ECM still requires basic timing information to derive the spark timing. On previous Commodores with electronic spark timing, this information was derived from a sensor driven by magnets on the flywheel. On the V6 motor, timing pulses are produced from a double Hall Effect sensor which monitors concentric toothed rings on the harmonic balancer (at the front of the engine). The outer ring has 18 equally spaced teeth while the inner ring has three "windows" of differing length at 120° intervals. The electronic control module determines the crankshaft position by measuring the number of voltage transi tions from the sensor on the 18-tooth ring during the period the other sensor "sees" a window on the inner ring. This crankshaft position information is fed from the DFI module to the ECM which then provides precise timing of the three ignition coils. 0 The electronic control module (ECM) uses surface mount custom microprocessor and co-processor ICs. The specially programmed EPROM module to suit it to the V6 engine is mounted on a socket at the bottom. Engine management Electronic instruments are used in the Commodore Calais. This is the back of the instrument panel showing the flexible printed wiring and three sockets for connection to the harness. free petrol (to replace the lubrication effects of lead tetra-ethyl) eventually cause contamination of the ceramic insulator which encloses the centre electrode. This contamination will lead to plug misfiring, hence the recommendation to replace plugs at 15,000km intervals. Claimed advantages of the AC Delco Direct Fire Ignition include no moving parts, less maintenance, no mechanical load on the engine, elimination of mechanical timing adjustments, more coil down time between sparks, and more time available to allow the ignition coils to saturate. As in previous Holden Commodores, there is no vacuum ad- Having explained how the double Hall Effect sensor monitors crankshaft position, we can list the other parameters monitored by the electronic control module. They are listed as follows: • Engine speed; • Manifold absolute pressure; • Manifold air temperature; • Engine coolant temperature; • Throttle position; • Exhaust gas oxygen content; • Battery voltage; • Park neutral switch position; • Vehicle speed; • Air conditioning 'on' or 'off'; • Engine detonation (using a knock sensor); • Cranking signal; • Auto transmission sump temperature; • Auto overdrive clutch 'on' or 'off'. With continuous monitoring of all the above parameters, the ECM controls the ignition system, as already mentioned, as well as the following systems: DECEMBER 1988 7 to 1 by monitoring the signal from an oxygen sensor mounted in the exhaust manifold and then optimising the amount of fuel fed via the solenoid-operated fuel injectors . In electronic terms, the engine management system is therefore a "closed loop" feedback system although at times it does operate in "open loop" mode. This can happen during idle, deceleration and starting. The electronic control module uses a custom microprocessor in conjunction with a a 16-bit coprocessor and 16K of random access memory. The module is the same as fitted to the current Group A Commodore V8, the JD Camira and the LD Astra/Pulsar series. It is customised to suit the V6 engine with a plug-in ROM (read only memory) module which General Motors refer to as a "Mem Cal" unit. Inside the cruise control module: on the left is the stepper motor which operates the throttle valve while at right is the microprocessor and stepper motor drive circuitry. The zirconia element oxygen sensor screws into the stainless steel exhaust manifold to provide feedback signals for the engine management system. It generates an output voltage at temperatures above 360°C. • • • • 8 Fuel system, consisting of the fuel injectors and electric fuel pumps; Idle air control; Auto transmission torque converter clutch; Air conditioner compressor clutch; SILICON CHIP • Radiator fan; • Diagnostics. The major purpose of the electronic control module (ECM) is to control exhaust emissions while maintaining good driveability and fuel economy. The ECM maintains the air/fuel ratio at precisely 14.7 Information sensors We've already talked about the Hall Effect sensor and toothed rings on the harmonic balancer. As well as providing the crankshaft position information for ignition timing, they also provide a measure of engine speed (RPM) for engine control as well as a signal for the tachometer which is an option on some vehicles. Let's now describe some of the other sensors. To obtain a measure of air flow in the inlet manifold, the V6 has a solid state pressure transducer. It also has a temperature sensor which is a negative temperature coefficient thermistor. At low temperatures it has a high resistance (around l00kO at - 40°C} while at high temperatures it has a low resistance (around 700 at 130°C). The throttle position sensor is a potentiometer connected to the butterfly valve on the throttle body. As with most of the sensors in the V6, it is fed with + 5V from the engine control module. The output of the throttle position sensor is zero at idle (when the butterfly valve is completely closed) and it increases to + 4.5 volts at wide open. The detonation sensor detects engine knocking. It is based on a vibration sensor (accelerometer) which puts out a voltage when it <at>HITACHI 20MHz/lmV $830 ExSa!esTax $996 me tax · ■· Wouldn't you pay a bit more for features like this? So good we give the full Spee! Display CRT Graticule Accelerating Potential External Intensity Modulation Vertical Deflection Sensitivity Bandwidth Rise Time o Quality Hitachi engineering O Two year Warranty o Includes two quality Hitachi probes o Tough all metal case and front panel o Ideal for servicemen - small footprint and light weight (31 Ox370x130mm 6kg) o Extensive triggering facilities including TV sync and vertical mode for steady traces when input frequencies differ widely o Free 55 page operating manual with circuit diagram MAX. Input Voltage Input Coupling Input Impedance Display Mode CHl Vertical Signal Output X -Y Operation· Sensitivity Bandwidth Phase Difference Horizontal Deflection Sweep Time Range Trigger Trigger Mode Trigger Source Trigger Sensitivity Order now. Call (02) 648 5455 32 Parramatta Rd, Lidcombe 2141 Fax (02)6471545 TelexAA24949 P.O.Box14Lidcombe2141 Melbourne (03) 480 0111 72-74 Chifley Drive, Preston 3072 Adelaide (08) 354 0588 Brisbane (07) 277 4422 Perth (09) 325 9333 Sydney ( BELL ] Bell Test & Measurement The measure of quality A Division of Bell-lRH Ltd (inc in N.S.W.) Prices subject to change without notice 6-inch rectangular. Internal , 8 x 10 div (1 div = 1 cm), Horiz onta l and vertical center lines further marked in 0.2 div increments, mark ing for measurement of rise tl me Trigger Coupling Trigger Slope Calibrator Power Supply Ambient Temperature Dimensions Weight MTBF Accessories Supplied 2 kV. Voltage : 5V o r more. Effect ive bandw idth : DC to 2 MHz. Max . inpu t voltage: 30V (DC+ AC peak }. 5m V/di v to 5V/div in 10 calibrated steps ± 3%. lmV/div, 2mV/d iv ± 5% when using x5 magnifier. Uncalibra ted co nt inuous control between steps 1 : < 2 .5. DC t o 20 MHz 1-3 dB }. DC to 7 MHz (- 3 dB) when using x5 magnifier . 17.5 ns. 50 ns when using x 5 magnifier . 300V {DC+ AC peak) or 500Vp-p AC at 1 kHz AC,GND, DC. 1Ml1 approx. 25 pF. CH1, CH2 {n ormal o r invert). ALT. CHOP , ADD Voltage : appro x . 20mV / div in t o 50!1 Bandwidth : 50 Hz t o 5 MH z (-3 dBi i nto 50!1. CH1 : X -a xi s. CH2 : Y -a xis. 5m V/div to 5V /div. lmV/ div, 2m V/div w hen using x5 magnifier. DC t o 500 k Hz 1- 3 dB ). 3" or less from DC to 50 k Hz . 0 .2 µs/ div t o 0.2s/div in f9 calibrated steps ±3%. 100 ns ± 5% w hen using x10 magnifier (20 ns and 50 ns uncatib rated ). Uncalibrated con ti nuous co ntrol between steps 1 : < 2.5. Automatic {sweep runs in absence of a triggering signa l and for signal below 30 Hz), Norma l {sweep runs when triggered ), TV' V, TV-H. CHl, CH2, V -MODE. Ex ternal, Line. 20 Hz to 2MHz 12 MHz to 20MHz I CH 1 an d CH 2 i 0 .5 di v I 1.5 div I 20mV I E,?C ternal I I 800rnV I AC. + or Square w ave. Vo ltage: 0.5 V ± 3%. Frequency: Approx . 1k Hz Vol t age : 100/ 120/220/240 V ± 10%. Frequency : 50/60 / 400 Hz. Power consumpti on : approx . 30 W. Rated range of use : +10 to 35° C. Limits of operation : 0 to 50° C. Storage and transport : - 20 to 70°C. 310IW) x 130IH) x 370ID) mm. 12.2 X 5. 1 X 14.6 in . Approx. 6 kg/ 13.2 lb. 20 ,000 hours for target value. Two AT-l 0AJ 1.5 pro bes, Fuse , Power cable , Operation manual. I i I the electrical pulse fed to the injectors. This varies between O and 11 milliseconds and happens normally once every crankshaft revolution. Control modes The compact V6 motor sits well back in the engine bay of the new Commodore. It has an uncluttered appearance due to the use of fuel injection and Holden's new Direct Fire Ignition system. detects vibration at around 6kHz with quite a narrow bandwidth of 500Hz. It is screwed into the lower front side of the engine block. If engine knocking (or pinging) is detected, the ECM responds by quickly reducing the ignition advance setting by 8 ° . When detonation stops, the ECM slowly restores the original ignition advance setting. The addition of the knock sensor is quite an improvement on the engine management of previous Commodores which had no way of varying their electronic spark timing if knocking did occur. The exhaust gas sensor is a zirconia element which is screwed into the exhaust manifold on the lefthand side of the engine. When the zirconia element is heated to temperatures above 360°C, it produces a voltage at its tip based on oxygen content, as compared to oxygen in the atmosphere. The vehicle speed is monitored by a 10-tooth wheel on the drive shaft. The toothed wheel is monitored by a Hall Effect sensor and the pulses it delivers are fed not only to the electronic control module but also to the instrument panel where they drive the analog speedometer and odometer. In the 10 SILICON CHIP Calais model, the odometer is based on a non-volatile RAM (ie, a memory which is not lost when battery voltage is removed). Fuel control The fuel system is based on solenoid operated fuel injectors made by Bosch. These are fed with fuel pressurised at between 235 and 320kPa, as regulated by the intake manifold pressure. A high manifold pressure, caused by a wide throttle opening, results in a high fuel pressure. A low manifold pressure, which results when the throttle is closed, gives a lower fuel pressure. In effect, the fuel pressure regulator maintains a constant pressure difference between the fuel line and the inlet manifold. This ensures that the fuel admitted by the injectors does not vary according to manifold vacuum. There are six injectors, located directly in front of each cylinder inlet port. They act as control valves and spray atomised fuel when they are electrically pulsed by the ECM. All six injectors are wired in parallel and so they are pulsed simultaneously. The amount of fuel delivered for each engine revolution is controlled by the length of We have already mentioned the "closed loop" control mode whereby the fuel/air mixture is maintained at the optimum for best working of the catalytic converter. There are times though, when this mode is not wanted, for example, during cranking. At these times the electronic control module works in open loop mode. In the starting mode for example, the ECM ignores the signals from the oxygen sensor and looks instead at the coolant temperature, to find out how hot or cold the engine is. It then sets the injector pulse width; ie, the length of time the injectors are turned on for each engine revolution. Depending on whether the engine is hot or cold, the injector pulse length will be between 8 and 115 milliseconds. If the engine is accidentally flooded with fuel, it can be started by pushing the accelerator pedal all the way to floor. The ECM then pulses the the injectors for only 8 milliseconds every crankshaft revolution, which has the effect of clearing the excess fuel. The ECM maintains this narrow pulse width as long as the throttle is open more than 98 % and the engine RPM is below 300. Once the engine starts, the ECM remains in the open loop mode until the following conditions are obtained: (1). The oxygen sensor has a varying output, indicating that the exhaust temperature is above 360°C; (2). The coolant temperature is above 44°C. (3). Engine not at idle. In the open loop mode the injector pulse width may well give an air/fuel ratio of more than 14.7 to 1. This can happen, for example, when the engine is cold and needs a richer mixture to drive without stalling. Acceleration mode When high acceleration is called for, the ECM notes the rapid change in throttle setting and in manifold The new Commodore has been completely tested to ensure electromagnetic compatibility for all its electronics. pressure and provides extra fuel by increasing the injector pulse width. If extreme acceleration is called for, the ECM may provide extra injector pulses during each engine revolution. During deceleration, the ECM can cut off the fuel supply completely for short periods, giving improved fuel economy. Fuel cut off occurs when all the following conditions are met: (1). The coolant temperature is above 56°C; (2). Engine speed above 1500 rpm; (3). Vehicle speed above 35km/h; (4). Throttle is closed; (5). Park/neutral input indicates "in gear" (auto transmission only); (6). Manifold pressure less than 20kPa. If fuel cut off is in effect, the fuel will be restored if any one of the following occurs: (1). Engine RPM drops below 1400. (2). Vehicle speed drops below 30km/h. (3). Throttle open at least 1 %. (4). Manifold pressure more than 20kpA. (5 ). Park/neutral input indicates "in gear" (auto transmission only); Fuel can also be cut off to protect the engine against over-revving. It cuts out for engine speeds above 5400 rpm and cuts back in again when engine revs drop below 5000 rpm. Battery voltage correction Another interesting wrinkle to the electronic control module is the battery voltage correction mode. If the battery voltage is low, the ignition system may deliver a weak spark and the injectors may be slower to respond to their short pulses. The ECM compensates for these potential problems by increasing the ignition dwell time, if the voltage is less than 12 volts, and increasing idle RPM and the injector pulse width if the voltage is less than 10 volts. Idle speed is something we haven't touched on yet but the ECM has control over this too, by varying the opening of the electrically controlled "idle air control" which bypasses the throttle valve when it is closed. The idle air control valve moves in steps from 0 to 255, corresponding to an 8-bit control system. Cruise control A trip computer and cruise control are fitted as standard on the Calais model and are an option on other Commodore models. The cruise control offers much the same facilities as those on competitive brands but it is of interest because it does not use inlet manifold vacuum to operate the throttle. Instead, it uses a stepper motor. General Motors cite a number of advantages in using the stepper motor, among them being the fact that the cruise control operation is not affected by changes in engine vacuum. In reality, since the cruise control employs a microprocessor, it is likely that the stepper motor lends itself better to more precise digital control. Driving the Commodore Part of the fun of preparing this report was a short test-drive of the car. Well, naturally the engine starts and runs extremely well and offers really sparkling acceleration. No doubt it will be the bestselling Commodore yet. Now, how can we scrape up the dollars to buy one? Acknowledgement Our thanks to Marc Mcinnes of General Motors Holdens Automotive Ltd and to Jack Stepanien for their assistance in the preparation of this report. '~ DECEMBER1988 11 DIC MITH Give Yourself A Christmas Present .. .from someone who cares! Includes bonus Mic. cat c-111& Yaesu's Budget FT747GX: IDEAL FIRST RIG! S 1395 Everything you need without the frills! Yaesu recognised the fact that amateur transceivers were getting out of the reach of the average person. So they did something about it: the FT747GX. A full 100 W with all amateur bands between 1.6 and 30MHz SSB CW AM and optional FM; receiver is 100kHz to 29.9999MHz continuous'. If ' you're looking for value along with performance, there's simply not a better rig than the FT-747GX: anywhere! Cat D-2930 Yaesu's Top Ender! Every amateur band from 50 to 1300MHz: that's some transceiver! It's All the way ... up to 1.2 gigs! Yaesu's superb all band, all mode VHF/UHF FT736R. It comes complete with the 2m and 70cm modules installed, you add the 6m or 26cm modules as you want them. Crossbanding and satellite modes - inbuilt. In fact, everything you need is there: IF shift and notch filters, wide/narrow IF filters for CW & FM, VOX, RF Speech Processor, Noise Blanker, 3-stage AGC . . . you name it, the FT736R has it. s2999 FT736R with 2m & 70cm: Cat D-2920 25W Output 6m plug-in module: Cat D-2921 5599 (10 W) 26cm plug-in module: Cat D-2922 s999 (10 W) (Introductory Price) - Stocks due late December. And the ultimate HF/VHF/UHF transceiver: fT767 GX With BONUS Microphonsl Combine the best features of the renowned FT757GX with the FT-726 and what do you have? The all band FT767GX. DC to light (well, almost) covering all HF, VHF and UHF bands up to and including 70cm! Sure, the FT767GX isn't cheap. In any sense of the word! It has all the features and performance you'd want from your amateur station because it IS a complete amateur station - in one! Cai D-2935 Nothing extra to buy: everytliing installed! s4 750 Save aver $300! • Every amateur band between 160m & 70cm! • A complete amateur station in one handy package! Bargain Antennas Portability Plus/ FT-290Mkll With BONUS ChargBr! 2M 5/8 Wave Vertical Tinr 2M HandHelil. Incredible performance!! 2M portability, versatility and performance at its best. The Yaseu FT-290 Mkll is just what Santa ordered for real amateur value! Features include All Mode (LSB, USB, CW & FM), 10 memories, 2.5W output, twin VFO's and much more. Yaesu's outstanding FT-23R puts into Cat D- 2875 a hand held all the features that once yllu'd need a monstrous bench model $ to achieve. Full 144 to 148 band coverage, 10 memories, fully microprocessor controlled, repeater WAS splits, high power and much more. Cat D-3490 Inc. FNB-10 NiCd 875 s949 Battery holder extra FT757GX II HF All Mode Computer aided transceiver technology at its best! There's no need for options with this one everything is built in ~all modes, all HF amateur bands, AM/FM, 600Hz narrow CW filter, iambic keyer, memory, 25KHz marker generator . .. the list goes on! Cat D-3492 Value plus! Quality whip 1.34 metres. Uses standard base. Cat D-4207 HF System Antennas All approximately 2m long, appropriately loaded and feature adjustable tuning. SOM Cat D-4310 40M Cat D-4311 20M Cat D-4312 NOW 5469 Heavy Duty Antenna Base Up To 5 Watts Output! To suit HF Antennas above. Cat D-4313 Just Save $20 and get up to 5 watts output from your FT-23R with our special offer on the FNB-11 600mAH battery pack. Available with any FT23R purchase! Save $20 . s79 If ,eurchased With FT-23R NEW Nearly $60 Valuef Why go to all the expense of VHF when most of your boating is close to the coast? Outstanding value and performance makes the Sea Simba the obvious choice. With 12 channels (10 fitted) including all 27MHz marine channels, 4 watts output, PA facility, RF gain control, ANL, etc, etc. Cat D-1718 Only s139ss 2m mobiles keep on getting smarter - and smaller. The FT211 RH proves it: and it's versatile! You can mount it overhead or under dash - and it gives 5 or 45 watts output on the entire 2m band. And this month only, you'll save a massive $70. What a great Christmas gift! Cat D-3494 5 1995 Limited Stocks Due In Shortly! s1495 12 Channel AM Marine FT212RH 2M FM TX (Cat C-116o) s3995 All only Was$499 Cat D-3496 With BONUS Microphone s14ss FREE with any Yaesu over $1001 729 5 High Quality and PBrformancBI All Mode, HugB Savings/ FRG-9600 VHF/UHF Receiver What a way to start your Christmas shopping SAVE $200! The sensational FRG-9600 is the ultimate scanner covering the complete 60 to 905MHz VHF/UHF spectrum. If ever you've dreamed about all the features you'd like in a scanner then this will make them a reality! Cat D-2825 Was $1199 Slashed to s999 With BONUS ChargBrl Bearcat 100XL Scanner Save $30 and get yourself a top performing scanner to boot! Features 16 channels, 9 band coverage, auto/manual search, selective scan delay, track tuning, priority channel, direct channel access .. . and there's more! Covers 66-BBMHz, 136-174MHz & 406-512MHz. Cat D-2813 Reduced to DSE AM CB Superb quality and performance at the lowest possible price! You won 't believe the features of this compact DSE AM CB. Comes with all 40 channels, full leQal power, built-in noise limiter, easy to read LED display, mic, mounting hardware ... and more. $ Cat D-1200 SaveS10 Exceptional Value! 89 369 5 These pages represent just a small selection of our amateur, marine, CB & scanner range. For the complete range, call into your nearest Dick Smith Electronics store today! • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 3871444 • Brookvale (Warringah Mall) 905 0441 • Campbetltown (046)2 7 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Goslord 25 0235 • Hornsby 477 6633 • Liverpool 600 9838 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800 • ACT• Fyshwick 80 4944 • VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 1614 • Ringwood 879 5338 • Springvale 54 7 0522 • OLD • Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • T-nsvHle 72 5722 • Unde!wood 341 0844 •SA• Adelaide City 232 1200 • Beverley 3471900 • SL Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 5W 6 Channel Hand-Held Marine Superb 27MHz hand held transceiver from Uniden! Features maximum legal power, all 6 channels fitted with marine frequencies - there 's nothing extra to buy! Plus you can connect it to your boat antenna and power supply for maximum performance. Cat D-1125 $20 OFF!! $ 169 s&~Jm VINTAGE RADIO By JOHN HILL Restoring the dial mechanism Almost without exception, the dial mechanism requires attention when restoring an old radio. The dial is usually the focal point of the set, so every effort should be made to restore it to original condition. There are three basic types of dial drive: cord, gear and friction. All give their fair share of trouble but can usually be restored to asnew condition with a little care and patience. With the cord-drive type, the cord either rots or wears through, thus disconnecting the tuning knob from the dial. The gear and friction drive types are frequently made inoperative by corrosion, wear and an accumulation of dust and grime. These problems must be rectified if a dial is to work smoothly once again. The best approach to any dial problem .is to completely strip the mechanism and thoroughly clean it. A common cause of stiffness in the mechanism is dried out grease on the moving parts, particularly on the track that the dial pointer slides along. Unless the dial unit is properly cleaned, this stiffness problem will remain. Cord dial drives In the case of cord dial drives, a sticky dial pointer may cause the cord to slip on the drive pulley. Proper cleaning really is important! Cord dial drives can vary from the simple to the annoyingly complicated. Some have cords and pulleys running everywhere. One particular model Radiola has four pulleys, with the cord making four passes across the front of the set. This dial mechanism uses at least a metre of dial cord. The dial cord itself is a rather special piece of string that has little or no stretch in it. This is an important characteristic because if the dial cord stretches with use, the dial pointer will gradmilly shift its relative position on the dial. Unfortunately, genuine dial cord seems to be unobtainable these days and one has to make do with substitutes. Although string can often be used for the job, the results are not usually very satisfactory. Dacron fishing line is by far the most suitable substitute for dial cord and may well be superior to the original cord. Many sports stores sell Dacron fishing line and a cord of about 0.5mm diameter is ideal. Perhaps the best advice one can offer regarding the restringing of cord dial drives is to make a sketch of the cord layout before removing the old cord. Such a sketch can be of great assistance and makes the task of replacing a dial cord much easier. Gear driven dials This huge full-width dial is from a post-war Kriesler console radio. The black and white photograph does not do it justice for it is one of the multi-layer types with a 3-D effect. Note the cast iron flywheel attached to the tuning spindle. 14 SILICON CHIP Gear driven dials usually don't give any trouble that a thorough clean and a few drops of oil can't cure, although there can be a few minor rumbles in the gear train. Most gear driven dials have a backlash eliminator of some type or other. This usually take the form of a split gear that is sprung in op- Vintage Radio Kits & Parts ORPHEIIS *RADIO* Gear driven dials don't usually cause much trouble hut should be given a thorough clean-up and lightly oiled. The spring on the pinion shaft acts as a backlash eliminator. Suppliers of • • • • • VALVES RADIO KITS CAPACIIDRS RESISIDRS BOOKS, ETC. Please send for our free catalogue ORPHEUS RADIO RSD B98 BALLARAT VICTORIA 3352 Ph. (053) 34 2513. Fax (053) 31 3412 FIX-A-KIT Kit Repairs - $1 5 per hour. Normal Rate - $30 per hour. No charge for kits that can't be repaired. 3 month Warranty on repairs. Construction - fixed or hourly rate . 1 2 Month Warranty on Manufactured Kits. This numbered gear driven dial is from the early 1930s and requires a lot of work to restore the lettering to original condition. Dials with station markings took over after about 1935. posite directions. When such a gear meshes with a normal gear there is no backlash at normal operating pressures. It is important when restoring a gear driven dial mechanism to make sure that the backlash eliminator is functioning properly. It could be locked up solid with dust or corrosion. When this is the case the eliminator must be freed up if it is to work as it was designed to smoothly and without backlash. Friction drive dials On the other hand, friction drive dials can be very troublesome and quite difficult to repair. Most friction types consist of a large semi-circular disc driven at its periphery by a pair of small spring-loaded driving flanges or washers. These washers eventually wear and this causes slip in the drive mechanism. Most old radios with friction dials will have slip problems somewhere or other. Custom Designing, Manufacturing, Large or Small Quantitites. HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment. (02) 633 5897 (02) 92 6309 Fax (02) 925 0840 DECEMBER 1988 15 The dial glass They don't make them like this any more - an ornate escutcheon from the early 1930s. If only the rest of the set was still attached. A "dial-a-station" dial from the· late 1930s. Like the pushbutton dials later used in car radios, these novelty tuning devices gave trouble and were not popular due to their additional cost. Once again, a thorough clean of the mechanism is an important first step and could free up the works enough to overcome the slipping problem. Nothing could be more detrimental to a friction drive mechanism than to force it to operate while all the parts are clogged up with dirt and corrosion. The previously mentioned driving flanges are usually the source of a slipping dial problem. If the flanges have not worn too much, they can be reversed and the dial will be good for years to come. However, in many instances, the 16 SILICON CHIP amount of wear both on the driving flanges and the semi-circular disc doesn't allow such an easy repair. When this is the case, a pair of slightly larger flanges are required and these will grip the worn disc in an unworn section and the dial will work once again. Friction drive dials often require considerable modification to bring them back to working order again. If you have access to a lathe, you can turn up special driving flanges of any size as well as doing other jobs that can get a radio restorer out of trouble. So much for the dial mechanisms. Now for the dial itself - ie, the glass plate with all the stations marked on it. There are several variations of the theme. Vintage dials vary considerably depending on their age. Early mechanisms (up to about 1935) usually have a numbered dial graduated from Oto 100. The dial is usually mounted behind a small escutcheon (dial surround or trim) with a pointer in it. The numbered dial itself is made of translucent plastic material similar to thick celluloid and will probably be backlit by a single lamp. Numbered dials were superseded by dials with the stations marked in their appropriate positions. The tuned station was indicated by a rotating or straightline dial pointer. These early glass dials were rather plain but that was soon to change. Later glass dials made use of colour and were much more attractive than earlier dials. The stations and other markings were placed onto the glass with a multi-coloured transfer so it's important to treat the glass with great care when cleaning it. During the late 1940s and early 1950s, the glass dials were replaced with plastic dials. These were very similar to the glass dials except for the use of acrylic sheet instead of glass. Unfortunately, acrylic sheet is inclined to craze and crack after 30 years or so and a radio of this type frequently shows its age for this reason. By far the most appealing dials are those of glass. Provided they have not been broken, they will look good for a long time. Some of the glass dials from the 1940s era were most spectacular. In some instances, they consisted of multiple layers of glass with various parts of the dial printed on different sections of glass. When all the layers were assembled, this technique produced a very pleasing 3-D effect where some markings of the dial seemed to stand out in front of other markings. It is obvious when looking at such elaborate dials that the dial was meant to be the focal point of the set. Restorers should keep this in Glass dials should be cleaned with care as some station markings can wipe off quite easily. If the markings are fragile, the best approach is to clean the glass with a moist cotton bud. It may even be safer not to clean the inside surface if it is reasonably clean. This view shows a numbered "peep-hole" dial on a set from the late 1920s. The dial was made of translucent material and backlit with a single lamp. mind. If one goes to the trouble of restoring an old radio, then every attention should be given to the dial in order to make it look as near new as possible. This means that everything should be clean and tidy and that includes the dial glass, its background, the pointer and the dial surround (or escutcheon). Cleaning the glass Cleaning the dial glass can range from an easy job to a most difficult one depending on how well the station markings are attached to the glass. Some dials are so tough they can be washed under running water and dried with a towel without doing damage. But do this to other dials and all that will be left is a sheet of plain glass. The best approach is to test clean the dial on an outside edge that is out of view when the dial is installed. Be careful - some dial markings are so fragile they can be removed with a single wipe. It is often the older, more valuable sets that have these super delicate dials - so don't say you weren't warned. Believe me, it's a rotten feeling when you discover that the station call signs have relocated themselves onto your cleaning rag. Perhaps the best way to clean ,some of these touchy dial glasses is to gently dodge around the markings with a moist cotton bud. It may even be safer not to clean the inside surface if it is reasonably clean. Many dials are mounted on thin rubber strips which become hard and brittle and usually break up when disturbed. Bicycle tube rubber is an easily obtained replacement. If the glass is remounted on fresh rubber strips, there is less likelihood of breaking the glass due to uneven pressure. When replacing a dial glass make sure that it goes back in the correct position in relation to the cabinet. Few things look worse than a crooked or poorly positioned dial. Dial pointers can always be brightened up with a touch of paint. Red, black and white seem to be the most common colours. Once again, a simple job such as repainting the dial pointer will give the dial that · new look and make the set more presentable. The dial's background is also an area that can require attention. This can vary from a simple wipe with a damp cloth to a dust down with a fine brush, a coat of paint or replacing a sheet of coloured paper. Once more, it is these little details that make all the difference. To finish off the job, the escutcheon will need to be cleaned and polished, whether it be metal or bakelite. Cleaning with hot soapy water and a nail brush should be sufficient in most cases. A bakelite escutcheon can be polished by giving it a good rub down with "Brasso" or some other fine abrasive metal polish. The Brasso treatment will restore bakelite and other plastics to new again. The fine abrasive action of the polish removes surface oxidation and brings up a good lustre. Brasso is also a useful cleaning and polishing agent for those moulded cellulose acetate dial "glasses" that are common on many old radios. Great care needs to be taken with these old dial covers because after 40 years or so they become very brittle and are easily cracked or broken if handled roughly. Next month's vintage radio topic will be on IF transformers and coils. ~ DECEMBER 1988 17 HIFIREVIEW Harman Kardon PM665Vxi 150 watt stereo amplifier Harman Kardon is back. Those who remember this quality brand, originally made in the USA, will be delighted to learn that Harman Kardon products are as good as ever and again available in Australia. To set the ball rolling we review their top of the line integr·ated amplifier, the PM665Vxi. By LEO SIMPSON Harman Kardon refer to their PM665Vxi amplifier as a high voltage/ high current design. Arguably, it is a high current amplifier, as it is rated to deliver peak currents to the loudspeakers of up to ± 80 amps. This enormous current capability is provided so that the amplifier can cope with speakers which have very low impedances when fed with dynamic signals (ie, music instead of steadystate sinewave signals). It is also a relatively high power amplifier, rated to deliver 150 18 SILICON CHIP watts per channel into 80 or 40 loads. That equal power rating into 80 or 40 loads is interesting because most amplifiers deliver quite a lot more power into 40 loads. This is a natural consequence of the fact that a power amplifier is a close approximation to a voltage source (ie, it has a very low output impedance) and therefore delivers more power into lower impedances. On the PM665Vxi, Harman Kardon have turned that convention around by providing two switches on the back panel, to select the load impedance, 40 or 80. We did not have a circuit of the unit at the time of writing but we deduce that the switches change the supply voltage to the output stage: high for 80, lower for 40. The reason for doing so becomes clear after the amplifier has been running for half an hour or so; it gets quite hot. Evidently it operates with a high quiescent current (ie, the current when no signal is present) as part of the Harman Kardon philosophy of designing their amplifiers with a minimum of negative feedback. By operating with a high quiescent current the amplifier will effectively be in class-A mode for most of the time and so will be inherently more linear: hence less need for negative feedback. However, because of the relatively high quiescent current the designers have then sought to an apparent difference to the amount of boost and cut available. In the hands of a knowledgeable user variable turnovers can be worthwhile but with average listeners they could be a source of confusion. For the latter people we'd suggest they select 200Hz and 2kHz and leave it at that. The purists are catered for too, of course, and the tone controls can be switched right out of circuit with the Tone Defeat switch. Capacitance trimming The interior of the PM665Vxi is dominated by two large finned heatsinks and by two large power transformers on the lefthand side. Both the cover and bottom panels are entirely covered with ventilation slots to dissipate the heat from the heatsinks. minimise the increase in power dissipation caused when the amplifier is actually driving the load. To do this, the supply voltage is reduced when 40 loads are to be driven. This also gives a margin of safety for the output transistors, especially when they are called upon to deliver the very high currents they are rated for. The PM665Vxi is a big beast. It measures 443mm wide, 134mm high and 398mm deep, including knobs, rubber feet and rear projections. It is heavy too, weighing in at 14.2kg. Harman Kardon styling is strictly conventional; finished in black, with fine gold lettering. Along the lower half of the front panel is a row of rotary controls while along the top is a row of tiny pushbuttons to engage various functions. All the usual functions are there plus a lot of others. In fact, it is probably one of the most feature-laden integrated amplifiers presently available. For example, the tape monitor switch doubles as a VCR selector so it switches video signals as well as the stereo audio signals from hifi or stereo VCRs. Dubbing between two VCRs or two tape decks is provided by the Record Out switch, which is right next to the Tape Monitor switch. Turnover switches A comparatively rare feature on integrated amplifiers these days is the provision of variable turnover on the bass and treble controls. "Turnover" refers to the 3dB (ie, half power) boost or cut frequency obtained when the tone controls are set to their maximum or minimum settings. On most stereo amplifiers the bass turnover frequency would be around 300Hz while the treble turnover would be around 2kHz. The PM665Vxi has pushbutton selectable turnovers at 200Hz and 400Hz for the Bass control and 2kHz and 6kHz for the Treble. Usually, changing the turnover frequency will not markedly affect the maximum amount of boost and cut at the upper and lower audible frequencies but it will make quite An even rarer feature on amplifiers is the provision of capacitance trimming for the moving magnet cartridge inputs. This is very worthwhile since the flatness of frequency response obtainable from magnetic cartridges can vary quite markedly, depending on the load capacitance. To give optimum flatness in the high frequency response some cartridges require 200pF of capacitance or less while others require up to 500pF or more. Typically, the leads from the turntable to the amplifier will provide about 100-150pF of capacitance in each channel while the preamplifier inputs will typically add another lO0pF or so. By contrast, the "Cap Trim" switch on the PM665Vxi gives input capacitance loadings of normal (125pF), + l00pF, + 200pF and + 300pF. This gives a minimum capacitance of 125pF and a maximum of 425pF, so if you know the capacitance recommended by the manufacturers of the cartridge, you can pick the closest setting. The Harman Kardon also has a pair of phono inputs to cater for moving coil cartridges, as selected by a small button to the right of the Volume control. Some larger integrated amplifiers can be split into separate preamplifier and power amplifier stages by pulling out ·a couple of · bridging links between two pairs of RCA sockets on the rear panel. On the PM665Vxi, the four sockets are there (labelled Pre-out and Main-in) but instead of the bridging links there is a switch on the front panel. Other small pushbuttons are provided for Loudness, Subsonic and High Cut filters, Mode (mono or DECEMBER1988 19 The PM665Vxi has comprehensive facilities and includes a number of RCA sockets with yellow centres to distinguish them as video inputs and outputs. Two slider switches (top right) are used to select the load impedance (either 40 or 80). stereo) and Mute. We should note, at this point, that it is hard to tell the settings of these buttons at a glance, especially if the lighting is dim, which is normally the case in typical living rooms. This is not helped by the very small printing for -the labelling on the front panel. We believe this is too small for most people to read easily. On the rear panel, there is the usual array of RCA sockets for input and output signals and there are a number of RCA sockets with yellow centres to distinguish them as video inputs and outputs. The speaker terminals are good, being those shrouded binding posts which will take heavy wires. These are better than the spring-loaded terminals found on many stereo amplifiers. Ventilation This amplifier is one that should not be stacked with other equipment because it needs plenty of ventilation. Both its cover and bottom panels are entirely covered with ventilation slots to dissipate the heat from the large internal heatsinks. Removing the top cover reveals more details of the interior which is dominated by the two large power transformers on the lefthand side of the chassis. These make the unit much heavier on the left and somewhat difficult to lift, for that reason. 20 SILICON CHIP Specifications Continuous power output Rated harmonic distortion Power bandwidth Output current capability Frequency response Signal-to-noise ratio (with respect to rated power, A-weighted) Phono overload (at 1 kHz) Filters Dimensions Weight Both transformers are wellshielded to cut down on hum leakage. They are fitted with copper straps and metal sheathing over the laminations. This is particularly important in an amplifier which has to handle video signals as well as low level audio signals. As far as we can tell without access to a circuit, the power supply appears to be quite conventional, employing 16,400µF of capacitance for both the positive and negative supply rails. Gleaning information about the power amplifiers is more difficult but the output stages appear to use high power Darlington 1 50W into 40 or 80 (both channels driven) 0 .08% into 80; 0 .1 % into 40 1 OHz to 1 OOkHz ± 80 amps peak 0.2Hz to 150kHz, -3dB 80dB phono {moving magnet) 76dB phono {moving coil) 98dB video/CD 11 OdB main in {power amp only} 220mV RMS {moving magnet); 12mV RMS (moving coil) 6kHz, 6d8/octave {high cut); 15Hz, 6d8/octave (subsonic) 443 x 134 x 398mm 14.2kg (ie, bipolar not Mosfet) transistors which have large plastic encapsulations. There are four such transistors in each channel. Wide bandwidth Harman Kardon have a policy of using discrete components throughout their circuits. This is necessary, apart from anything else, because this company is noted for designing its amplifiers with very wide bandwidth. This amplifier certainly follows that philosophy. The frequency response from the high level inputs is quoted as 0.2Hz to 150kHz, at - 3dB points, at a power level of 1 watt. Similarly, the half-power bandwidth is quoted at lOHz to lOOkHz. These figures are quite exceptional. We had no trouble in confirming them. SPECTACULAR ELEASE vHa Performance Rated power output from the PM665Vxi is quoted at 150 watts per channel into 80 or 40, with both channels driven. Rated harmonic distortion is less than .08 % for 80 loads and less than 0.1 % for 40 loads. Our tests easily confirmed the power output although the typical distortion figures were somewhat better than those claimed. We measured around .02% across the board. Actually, a harmonic distortion figure of .02 % is not particularly low these days and competitive amplifiers would measure considerably better. However, Harman Kardon's figure is to be expected, as a result of designing the amplifier with a mm1mum of negative feedback. Even so, a figure of .02% is still very respectable. Rather than go through each performance parameter we can report that we were able to confirm all the other specifications listed in the separate panel. The telling is much quicker than the doing, of course, as it takes almost a whole day to confirm all the specs in a comprehensive integrated amplifier such as this. Sound quality And what about sound quality? It's every bit as good as you'd expect a top quality amplifier to be. With its comprehensive control facilities, bags of power, solid construction and conservative design, it is sure to give many years of musical satisfaction. If you're in the market for a new stereo amplifier, you should give the Harman Kardon range a careful audition. Recommended retail price for the Harman Kardon PM665Vxi is $1995. For further information, contact the Australian distributors Convoy International Pty Ltd, 400 Botany Road, Alexandria NSW 2015. Phone (02) 698 7300. ~ NEWSA-100 SPEAKER KIT Since the introduction of VIFA speaker kits in Australia in 1985, thousands of speakers have been built with superb results. VIFA is now proud to release four new speaker kits ranging from a mere $399 to $1199 per pair including cabinets. Never before have speaker kits been so popular in Australia than after the heavy devaluation of the dollar. Similar fully imported quality loudspeakers are today typically 2-2½ times more expensive. And these speakers may very well be using Danish VIFA drivers anyway, as VIFA supply more than 50 of the world's most respected loudspeaker manufacturers with drivers. But why the big savings? Because fully imported speakers suffer from 25% import duty, 20-30% freight, 30% sales tax and 28% handling charges (typically). So if you would rather put your money into better quality than in other people's pockets, VIFA speaker kits are the only way to go. Are they difficult to build? No, the kits are supplied with all parts needed including fully built crossovers and pre-cut flatpack cabinets ready to assemble. No soldering or carpentry skills are needed, just a Phillips head screwdriver, some simple hand tools and a few hours of your leisure time. Are they as good as people say? Read the reviews, listen and compare with any other speakers twice the price or more. Need we say anymore? VIFA for the quality conscious audiophile. For full details please contact Sole Australian Distributor: SCAN AUDIO Pty. Ltd. P.O. Box 242, Hawthorn 3122. Fax (03)4299309 Phone: 4292199 (Melbourne) (02 5225697 (Sydney) (0 3577433 (Brisbane) (09 3224409 (Perth) Stocked by leading stores throughout Australia (O! Polystyrene capacitors YES Made here in Australia? YES Made Special to Type? YES Where From? Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors . Why design circuitry which requires additional components to achieve a specific capacitance ; we can wind exactly the capacitance you need to match your design criteria within the ranges of 1OpF to 1 µF and up to 10,000VDC. Capacitors are manufactured to 0 .25%, 0.5%, 1.0%, 2.0% , 2.5% , 5%, 10% and 20% and are priced according to tolerance. All capacitors are tested to 2.5 times the rated voltage. ~--wwwwwwwwww · Interested? Call us now on: (02) 938 4690 OR Cut out and post this coupon to Post Office Box 7 40 Brookvale, N.S. W. 2100 I Yes, I am interested in your capacitors. I Please post me details of the following values: . .. I . .. VDC ... I . . . VDC ... I . .. VDC . .. I . . . VDC . Name (Please print) Address ~-------------~-~~~~~~~~~~~J DECEMBER1988 21 GEL BATTERY SURPLUS BARGAIN We have purchased a quantity of Natklnal brand 6 volt Gel rechargeable batteries. These are ideal for burglar alarms, or where any back-up power supply is n99ded. Connect two in series to give 12 volt. Two sizes available: 2.4 AMP 6 VOLT Cat. SB-2490 $9.95 5+ $8.95 ea 8 AMP 6 VOLT Cat. SB-2492 $24.95 5+ $22.50 ea Japanese made 2.4A size: 98.5(H)x66(L)x33(W)m BA size: 94(H)x151(L)x50(W)mm Another surplus stock buy. These are a high quality black thermoplastic PCB terminal strip. As used by the alarm Industry. Available In 4 way and 1O way. Units are supplied unasserrbled • I.e. you have to screw the screws In. Normal Price 10+ 100+ 4way $2.50 $1.50 $1 .30 Cat. HM-3204 10 way $4.95 $2.00 $1.80 $1.50 Cat. HM-3205 BELOW WH,OLESALE PRICE ' . 4 WAY PCB TERMINAL BLOCK Limited quantity, surplus purchase. Solder direct to PCB and connect wires, NORMALLY $1.75 Cat. HM-3174 SPECIAL PRICE $1.00 each DIGITAL PANEL METER CATALOGUE A brand new 18 page Lascar catalogue Is available from the Australian representative, Jaycar Electronics. The catalogue features the latest Surface Mount Technology DPM's from Lascar • the world's leading DPM manufaclurer. Panel meters are available in both liquid crystal and LED-type displays. All DPM's come complete with snap-on bezels. Full technical information Is provided for the 50-odd products described. Contact Jaycar branches or Hea d Off.Ice for a free copy Of the c:atalogue. --~p-------------1 A JAYCAR/SILICON CHIP EXCLUSIVE KIT PLASMA DISCHARGE DISPLAY Ref: Silicon Chip August 1988 Jaycar and Silicon Chip have corrbined to produce a klw cost but spectacular plasma discharge display. The Jaycar kit of this project includes the rare-earth chamber, mounting plinth, EHT transforrrer and Inverter electronics. A 2-3 arrp 12v DC power supply is required. (A battery charger is ideal). Call in to one of our stores forademol ~(l!)(!Dll!l!J.W8' ~ AA Ni Cads ;~::~~ - $3.50 each or 4 for $12.50 A.11J]D)II(O) A.lMIIP' Til) J.\ TO) tM J.\ TTIC'J Don't waste money. Buy rechargeable NiCads, 450mA. Quality brand. Cat. SB-2452 .I..C)~l.l,ll'~.!.'-J Completely built, this module measures 63 x 35mm, has a high Input impedance and high gain. Runs on 9V and requires a 15 ohm load. Supplied with full specs and data. Made In England! Cat.M-02920NL 4f OLD NI Cad BATTERIES ARE DANGEROUS Y $3.95 Bring in your worn-out NiCads in December and we will dispose of them safely for you. As a bonus we will give you a 5% trade-in allowance on new onesl 10+ $3.50 each We have a small quantity of 15 ohms· x 4" speakers to suit. Otherwise just use two 8 ohm speakers in series. Cat. AS-3013 $3.95 DECEMBER ONLY (Don't forget • all those toys use lots of battery power!) Cat. KC-5035 ,. NEW LOW PRICE $229 SAVE $70 UHF TUNER Sanyo Model T1087RA Yet another scoop purchase A compact high quality tuner that operates from 526-814MHz (corresponding to channels 28 thru 63). This tuner is designed for Australian standard reception (AS1053 1973), and Is offered at a very low price. Knob not supplied. Cat. DM-1000 NORMALLY $29.95 SAVE $15.00 THIS IS RARE! WAS$299 Savings mad of mass prod Tonearm cable. Yes, we've finally been able to locate a small quantity of 4 core tonearm cable. This cable is twisted together and total diarreter is approx. 2mm. 1 metre length. Cat. WH-3035 $2 tdoor Inl"ra Red Motion Detector al for both residentiM ~ a comrrerc1a1 apllcatlons. Completely self contained and asy to Install. Designed to mount directly standard round junctkln box. he unit will automatically turn on two odlights when sorreone walks within the elector range. Ideal security system to rotect loved ones and property. Detection nge is 40 1881 long by 60 1881 wide. Light ill stay on for a minimum of 1Oseconds u 15 minutes (adjustable). Works only at ight. Globes not supplied. at. LA-5t32 NEW'88 NLY $139 12V CAR ANALOGUE CLOCK MOVEMENT MASSIVE SCOOP PURCHASE! Grab a quartz crystal car clock with a set of automotive style hands at a price that will astonish you I Once again our suppliers huge loss Is your gain I Convert that broken/ unreliable or inaccurate mechanical clock in your car to space age precision I Made In West Germany by VDO, the module measures roughly 45 x 38 x 40 deep. The compact size virtually ensures that It will fit In anyspacel Quantity strictly limltedl Cat. XC-0108 ONLY $9.95 "PLASTI-DIP" Heavy Duty Flexible Liquid Coating BACK AGAIN! White Cone Midrange Our most popular midrange. Large sealed back with extra clear crsip midrange. 110mm, 80 watts RMS power handling, 95dB sensitivity, 10oz magnet, freq . rasp. 31 Hz• 7kHz, resonant freq . 310Hz. Cat. CM-2080 1986 PRICE eat your heart out Dickll ONLY $22.5 Plastic Dip Is an air dry liquid plastic coating that produces a tough, thick pliable finish. It Is Ideal for making a pliable coating for the handles of tools, etc. Supplied In a 470ml dipping can. WIii do dozens of tools. Cat. NP-1100 RED IN COLOUR ,,. 0 NL Y $24 .95 NEW'88 ;j ,,-.,,;;:"1""'":"=-.:,...,I , . \;/1','P :.:.;~..:-:~-· .~~i;;.::,~ __;.-· Piezo Tweeter ,"l Polypropolene Cone Midrange 6 WAY POWER OUTLET _WITH MAINS FILTER We've been able to lower our pri,:e on our Not only Is It a 6 way power board, it incorporates a voltage surge and spike protector and noise rejection filter network. Supplied with 2 metre cord and mains plug, safety shutters on each outlet. Illuminated master on/off switcvh and even a safety circuit breaker. Cat. MS-4000 high power midrange. Black Poly cone. Huge 10oz magnet. 5" diameter. Specifications: Power handling 100 watts RMS system Resonant Freq. 570Hz Sensitivity 96dB Freq. Rasp. 570Hz • 7kHz Cat. CM-2085 At last, an economical priced quallty piezo tweeter. Another manufacturers surplus stock purchase by Jaycar. These are in other catalogues for $18.951 SPECIFICATIONS • Frequency response 3.5kHz-40kHz • SPL 94dB/1W at 1 metre • lntermiitent peak power 100 watts • Size 78mm square • Use with or without crossovers Cat. CT-1905 UNREAL PRICE 9.9 $59.95 PASSIVE INFRA RED DETECTOR - PRICE BREAKTHROUGH It had to happenll Jaycar was the first to offer pulse count PIR's and lately we were the first to offer pulse count for less than $100. We are proud to announce another first In PIR's. A QUALITY PIR FOR ONLY $69.95 FULL PRICE Sure, you are probably thinking "but what about the quality and reliability". There's nothing worse than an alarm system that false triggers, you know the old story about the boy who cried won. We have extensively tested the units and have no doubt about their quality and operation ability. Features & Specifications • Dual element pyroelectric sensor • 24 dual element detection zones In three layers • Wide angle 90" multi layer coverage • 12 metre range • Operation voltage 7.5 • 16V DC • TaJTl)0r protected • LED Indication • Size 65(H) x 84(WJ x 46(D)mm • Colour beige • Relay output • 3 month guarantee Cat. LA-5017 NLY$69.95 $30 LESS THAN ANY PIR WE KNOW OF NOTE: If you require absolute mains suppression don't forget our Australian made Squeaky Clean Mains Filters. SAVE ON ADCOLA CONE TWEETER SOLDERING;· The newest ediUon to our speaker range. ~~!!u~~~~ecs BASE STATION NORMALLY $159.50 / SAVE $20 , DECEMBER PRICE $139.50 Cat. TS-1475 40W IRON • CT6 NORMALLY $49.95 SAVE$5 NOW ONLY $44.95 70mm cone tweeter. Norn lrrpedance 8 ohms Max power 75 watts Freq. Range 3kHz • 18kHz Sensitivity 91 .5dB Flux density 7,200 Gauss Magnet size 45(dia) x 22(dia) x 9mm Magnet Weight 47.4 grams Net Weight 170 grams Cat. CT-2000 WAS $11.95 Another surplus stock purchase. The quality is first class, the only problem is the colour. It would have been totally In vogue In the 1950's or 60's, but It's not really suited to the loungerooms of the SO's. If you have speakers In the rumpus room, garage, boys room etc.. that require cloth then this cloth Is Ideal'. Oh, we haven't told you about the colour yeti 'It Is also ideal if you REALLY want to be MEGA trendy! SAVE$2 NOW$9.9 Cat. TS-1478 BOW IRON - CT7 NORMALLY $55.00 SAVE$7.50 NOW ONLY $47.50 Cat. TS-1480 -~~-•I STYLE 1 Gold with black strips at about 1 Jaycar Introduces the Easy way to Buy Greencaps Don't aver run short of that greencap again. 5 easy to buy, low cost packs which represents a considerable saving over individual prices. Each pack contains 1O of each value and packs cover the complete range from 0.001uFto0.1uF. Values: (10of each) 0.001, 0.0012,0.0015, 0.0018, 0.0022 A GREAT $6.95 TOTAL 50 pieces Cat. RG-5000 Values: (10 of each) 0.0027, 0.0033, o.0039, 0.0047, 0.0056 TOTAL 50 pieces Cat. RG- 5001 $6.95 Values: (10 of each) 0.0068, 0.0082, 0.01, 0.012, 0.015 $6.95 TOTAL 50 pieces Cat. RG-5002 Values: (10 of each) 0.018, 0.022. 0.021, 0.033, o.039 $6.95 TOTAL 50 pieces Cat. RG-5003 Values: (10 of each) 0.047, 0.056, 0.068, 0.082, 0.1 TOTAL 50 pieces Cat. RG-5004 "CRIME STORY" SPEAKER CLOTH SALE $9.95 WA y TO NEVER BE OUT OF THAT ODD GREENCAP AND KSEATVEATA SAME TIME %i 1/2"1ntervals.Slze5'x1mt Cat. CF-2756 $3 • 95 SAVE $1 O STYLE 2 Gold with gold reflective pieces through It. Size 3' x 1mt. Cat.CF-2757 $2.95 SAVE $7 STYLE 3 It's a bit more down to earth. It's brown with red, black and green fleck. Size 3' X 1ml. Cat. CF-2758 $3.95 SAVE $6 132 pages of electronic goodl86. tt you doni have our catalogue or nyoU've lost It call In to any of our showrooms for a free copy. (And a lollie n you have to wait). OR send a large SAE to PO Box 185 Concord 2137 and we'll post you one. 0.1 MONOLITHIC CAP SALE We have available a pack of 0.1 monolithic capacitors with short leads at a very special price. The only catch is that they have cut leads ready for machine placing In PC boards. The leads are about 1.5mm long • just long enough to go through a circuit board. ONLY $7.95 for 100 NORMALLY $16.50 per 100 00"' - GOVERNMENT INSTRlJ!\ffNTALl"flES, SCHOOLS, PlJIIUC COMPANIES IF YOU WISH TO PURCHASE l'RO'.\I t:s, SIMPLY SEND US YOUR OFFICIAi , ORDER AND WE \\'ILL <;IVE YOli A COMPl,EMENTARY 30 DAY ACCOl :NT. CLOCK MOVEMENTS WITH BUILT-IN MELODY MODULE No more messy, separate modules. All in the one easy to mount housing. TWO MODULES are available. Both chime the hour after playing their tune. XC-0106 plays Westminster Chimes each hour then gongs the hour (I.e. 7pm - 7 gongs). XC0107 plays a different melody each hour then gongs the hour. Both units are supplied with: • Clock movement • Speaker and battery holder • Hook to hang up • 3 sets of hands Cat. XC-0106 Westminster chimes/clock movement Cat. XC-010712 melodies/clock movement SAVE$12.95overseparateclockmovementandchimes SOLAR PANELS 2Models 6 volts <at> 240m.A 12 volts <at> 120m.A Each panel measures 327(L) x 165(W) x 18mmthick. Cat. ZM-9008 LOUO!,,J1.AKJJ\ l~C"ll)\"\1"f" DISICN ANO OON~TkUCT10N - $79 Cat. ZM-9009 $79 Solar Battery Charger ONL V 18.95 ea Loudspeaker P.A. Bin Enclosure Designs Book - 12 volt panel<at> 120mA 6 volt panel <at> 240mA Fane Acoustics UK, makers of speakers for the likes of Pink Floyd, David Bowie, Genesis, Iron Maiden etc. have produced an absolutely fantastic book on P.A. bin designs. The book begins with construction info in general, I.e. what materials to use, how to join timber, how to brace the cabinets, sealing, lining, wiring, crossovers, impedance matching, etc. The second section includes 22 separate detailed designs for: reflex cabinets, horns, wedge monitors, folded horns, w bins etc. Designs accommodate 1O", 12", 15" and 18" speaker components. m• jjM,•-. The solar panel In the lid will charge up to 4 x M N!Cads In a fairly short time. It is Ideal for yachts, carrpers or anywhere where 240V Is not available. Cat. MB-3502 Size: 65(W) x 30(H) x 95(D)mm WAS$17.95 0.45 VOLT SOLAR CELL MODULES SOLAR PLANT TURNTABLE No more lopsided plants. WIii handle up to 15 kg of weight. Also ideal for store windowdisplays. Cat. YX-2503 $ _ 17 95 $14.95 l Cat. BF-4150 Brand New 240V 50Hz Synchronous Motors We have made a SCOOP PURCHASE of Double Pole Squirrel Cage motors with I 8 rubber shock mounting plate (which can be removed if necessary). The motor is supplied with an on/off switch (also removable) and features a 4mm diameter hard steel drive shaft, 21 mm long (with mounting plate removed). These motors are ideal for fans or when reduced , in applications requiring a fractional HP drive, Cat. YM-2708 - • NOW $14.95 Connect in series or parallel. Two sizes. 0.45V 0.45V 75x45x6mm 96x65x6mm Cat. ZM-9005 Cat. ZM-9006 $3.95 10+ $3.75 - $6.50 10+ $6.20 Dear Customer There are times when due to circumstances beyond our control some advertised products may not be in stock when our ads appear. We suggest you phone to check availability. • . SOLAR, EDUCATION KIT WAS $10 NOW ONLY $5 Our solar education kit is designed to let you build your own solar models. This kit comes complete with : • Solar cell module • Solar energy booklet explaining the whys and hows of solar energy • Small DC motor • Screws and nuts • Wire with motor clips • Coloured spinner discs • Paper aeroplane and bird models • Plastic turntables with 4 sizes, 5/8", Cat. KJ-6690 1', 1 1/2" and 2" • Plastic fan-spinner ~ ~ FOSTER DOME TWEETER - BACK IN STOCK! The D025N25 is a brilliant tweeter. It's probably the cleanest sounding tweeter we sell. It handles enormous amounts of power and has a very smooth response, Power Handling 150 watts RMS system Freq. Response 3kHx-30kHz Resonant Freq. 1,200Hz Impedance 8 ohms SPL 91d8/1 metre Flux Density 13,500 Gauss Weight 610 grams Cat. CT-2018 ONLY $9.95 SOLAR CAR BATTERY BOOSTER Keeps your battery charged in your car when you are not using it. Cat. MB-3503 $29.95 $36.50 12" GUITAR SPEAKER Finally available, our updated guitar speaker with extended frequency response. Especially suited for not only bass guitar but rythm and lead as well. Resonant Freq. 60Hz (was 80Hz) Impedance 8 ohms Freq. Response 80Hz - 5kHz Power Handling 100 watts RMS Magnet Weight 40oz Net Weight ·, 3610 grams Sensitivity \ 102dB But the best news is the price· NO INCREASE Cat. CG-2380 DISCOLITE KIT Ref: Silicon Chip July 1988 Build your own light show Cat. KC-5032 "EASY ETCH" Engraver $159.5Q " ' ~ ' _, !¥: r:·-:~-. . ~ " "' Features • Pulse count • 48 beams • Sliding PCB • Hallway lens optional (Cat. LA-5020 $3.95) WAS $119 CARLINGFORD STORE HAS MOVED TO PARRAMATTA AT355 CHURCH STREET (Cnr Victoria Avenue) SAVE $20 NOW $99 - at last a low cost engraver I Ideal for permanently marking your valuables with owner identttication. As ideal for that everlasting message on gifts and trophies. Features: • Supplied with hardened steel engraving kit• will engrave virtually any surface • rotary motion of engraving kit eliminates vibrations • Works at safe 12V (adaptor supplied) • Diamond engraving bit available (Cat. TH-1908 $23,95) . (Cat. TH-1912 $10.95) Cat. TH-1920 JAYCAR-Nol FOR KITS Protector Car Alarm Ref: Silicon Chip Feb 1988 About every feature you could ever want In a car alarm. See our 1988 catalogue for full details. Extras not included in kit: Back-up battery Cat. SB-2490 $22.50 ; Piezo siren Cat. LA-5255 $17.95; 12 volt siren Cat. LA-5700 $26.50. Cat. KC-5021 $79.50 Remote Control (Full kit) Ref: Silicon Chip March 1988 Full form version. Kit includes all compcnents except box for receiver, piezo siren and piezo transducer and battery for transmitter. These items are available separately: Transducer Cat. AB-3440 $2.75; Piezo Cat. LA-5255 $17.95; Battery (pkt 2) Cat. SB-2420 $3. 75 Cat. KC-5034 JAYCAR BRAND NEW MINI TOGGLE SWITCHES Economy Soldering Iron Quallty mini switches with black plattened actuator. Rated at 6A 125V, available In a single and double pole styles. SPDT Cat. ST-0546 $3.25 ea DPDT 25 watt general purpose iron. Ideal for beginners. Generous mains power cord. Supplied on attractive card with soldering Instructions on the back. Cat. TS-1450 10+ $3.00 ea Cat. ST-0547 ONLY $16.95 $3.75 ea 10+$3.S0ea ULTRA MINI TOGGLE SWITCHES Conical spare tip Cat. TS-1453 $4.95 24 HOUR: Switch an appllance"ON" and "OFF" up to 24 times In any 24 hoursl Uses simple analogue dial with program pins (8 pins supplied which means that extra pins are required for more than 8 operations/ day). It Is VERY easy to set and operate - as opposed to programmable digital types I It also has a manual override that does not affect original program setting. 12 month warranty. Cat. XW-0400 $23.95 Ultra small size. Body only 8mm x 9mm (DP version) and 8mm x 5mm (SP version) Rated at 3A 125V. SPDT Cat. ST-0540 $2.20 ea 10+ $2.00 ea DPDT Plug-In TIME SWITCHES Metal Stand to suit Jaycar Soldering lorn Sturdy metal base with sprung stand and heat resistant ferrule holder. Cat. TS-1500 Cat. ST-0542 $2.60 ea 10+ $2.40 ea $10.95 $79.50 Tip cleaning sponge to suit Cat. TS-1552 95e (Compare that price with the Weller sponge 7 DAY: Can switch "ON" and "OFF" up to 42 times a week al two hour intervals (16 4 --c~t~~~;h~:~~~~~~~:~ ~ ~1 ~ u~ o~:w~ev~- '-: ;r~:· "'I Wiioiiri:ks:'.a_n_d POL YSWITCHES Low cost reliable speaker protection. Refer articles In Electronics Australia July '86. RN3410 is suitable for protection of tweeters In systems up to 100 watts. It's rated at 50 volt and 0.5 arrp. Nominal resistance Is 0.4 Ohms Cat. RN-3410 (R.D.E. 050) $6.95 ea 1O+ $6.65 ea 12V ILLUMINATED PUSH BUTTON Jaycar 12V 30W Soldering Iron Economy push on/push off with large RED (20x20mm) actuator with a chrome surround. Perteet for fake car burglar alarms. Rated 12V 1O arrp 3 pole. Cat. SP-0745 Ideal marine use. Has car cigarette lighter plug for convenience. Extra long cord. Cat. TS-1470 ONLY $6.95 ONLY $11.50 •---------------t Motorised Siren still the ultimate noise maker RN3415 will protecl midrange and woofer upto 100watts. Rated at SO volt and 1.16 amps. Nominal resistance is 0.12 Ohms. Cat. RN-3415 (R.D.E. 115) When your car alarm goes off you want EVERYONE to know about ill Many car alarms these days make the same 'electronic' noise that is Increasingly being Ignored. This motorised siren makes a racket like the old police cars of the 60's & 70's. You would have heard the noise when the air-raid sirens came on In old WWII movies. EVERYBODY takes notice! Grab one now at the never-to-be-repeated price of only $25. Cat. LA-5280 NORMALLY ABOUT $70 $6.95 ea 1O+ $6.65 ea RN3418 Is rated at 50 volt at 2.45 amps. Nominal resistance is 0.039 Ohms. As used in 100 watt amp.module Cat. KC-5019 from Silicon Chip December 1987. $8~95e~D10:A$8.25 ea 1 NEW LOWER PRICES ONLY $25 SMOKELESS ASHTRAY In this day and age, cigarette smoking is becoming socially unacceptable. This product will help the poor old smoker by removing all smoke from a cigarette sitting in the ashtray. It works like thls:Switch the unit on, and It will just sit there in the off mode. When you "light up" simply tap the ashtray and it turns on and rusn for 10 minutes before going back to the standby mode. The unit has a silent motor which draws the smoke insidend through activated charcoal layers to purffy the air. Operates on 2-C size batteries or a 3V DC power source. The ashtray section (where the cigarette sits) is made from Melamine and just lifts out to empty and clean. Stock Is expected early In December In time for Christmas. Size: 125mm x 125mm x 75mm. oNXLv:,s14.ss y $229 STUDIO 200 HI FI PREAMP Ref: Silicon Chip June/July 1988. Excellent quality at a modest price Cat. KC-5033 gr Ott; 1 _ M ~-· ff HEAD OFFICE 21 37 MAIL ORDERS POST & PACKIN 10 5 8 •_[_::_i_i~_1l_~_1_1_:'_::__;_d;_!_}_:_:_!1______~_t_R~-~-1~_~-~s-:~_~_r_i:.:_!_! . _:_:B___, ....~ER_s_1oo_l_i_H_I_J_oi_o______ ■ s VISA MAIL ORDER VIA YOUR ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY - CITY 117YorkSt. (02) 2671614- GORE HILL 188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 Mon-Fri 9 - 5.30 Sat 9 - 4pm PARRAMATTA BURANDAQLD 144 Lo9an Rd (07) 393 0777 Mon-Fn 9 - 5.30 fhurs 8.30 - Sat 9 -12 Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 -12 355 Crorch SI (Cnr. Victoria Rd) (02) 683 33n Mon-Fri 9 • 5.30 Thurs 8.30 pm - Sat 9 - 2pm 115 Parramatta Rd (02) 745 30n Mon-Fri 8.30 - 5.30 - Sat 8.30 -12 MELBOURNE-CITY Shop 2, 45 A'Beckett St City (03) 663 2030 121 Forest Rd (02) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 -12 SPRINGVALE VIC Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2· 120W public address amplifier Today's public address amplifiers are a real challenge to the designer. They need to combine very high sensitivity for low impedance microphones, mixing for several inputs, tone controls and high power output. The high power design presented here is our response to that challenge. By LEO SIMPSON & BOB FLYNN We have had quite a number of requests for an amplifier design for public address applications. Our first step in meeting those requests was to design the rugged power amp module presented in the November 1988 issue. In this issue, we present the microphone preamplifier and mixer stages and show how to assemble them onto a printed circuit board. Two low impedance microphone inputs are provided and they can be 26 SILICON CHIP connected as balanced inputs via 3-pin XLR sockets or as unbalanced inputs via 6.5mm jack sockets. In addition, there are two stereo line inputs which means that any program source such as a CD player, cassette deck or FM tuner may be connected. Mixing of these four sources (ie, two microphones and two stereo line sources) is provided via four knobs on the front panel. The other front panel controls are bass and treble controls and the master volume control. With 120 watts RMS power output, this public address amplifier will be suitable for a wide range of installations. It could be permanently set up in buildings such as halls or churches or used in temporary installations where AC mains power is available. Performance Traditionally, public address amplifiers have not had low noise, low distortion and a very flat frequency response. They have tended to be very utilitarian affairs with more of an emphasis on reliability than on good sound quality. We have taken a conservative approach to the design of this amplifier, to ensure stability and to prevent RF breakthrough. Even so, the overall performance is rather better than from run-of-the-mill PA amps. +20 ~ +10 TREBLE BOOST BASS BOOST ~I'-- ... / V ' ..... ,/ .,,v -20 20 .......... /"" "'-.... ~ ,/ / ,..... .... -10 ,- I..--' ......... V / -- / ...... _.,,/ --- Fl ~T -............ ' / r--..... ' ...., ... TREBLE CUT BASS CUT Fig.I: this diagram .shows the frequency response of the amplifier with tone controls flat and the effect of each control when at the maximum or minimum setting. Note that there is a small amount of interaction between the controls at mid frequencies. ~ ./ I 100 I I HERTZ Part of the reason for this is the excellent performance from the two toroidal transformers, one for the power supply and one for the 1OOV line output. Not only do both transformers have low external radiation but the line transformer is exceptionally good for its flat frequency response and clean output waveform. If we'd had to depend on conventional transformers to obtain the same performance, the amplifier would have been a great deal heavier and probably bulkier too. All the performance details are summarised in the accompanying specification panel. Preamp and mixer circuitry Now have a look at the complete circuit of the PA amplifier as shown in Fig.1. For each of the balanced microphone inputs we have used a low noise LM833 dual op amp. This is shown in the top lefthand corner of the circuit. The LM833 dual op amp is depicted as IC1a and IC1b which are connected together as a balanced input stage. 1 % metal film resistors are specified in the balanced input stages, firstly to ensure low noise and secondly to ensure good "common mode" rejection. Common mode signals are those extraneous signals which balanced inputs are intended to reject; eg, hum, mains hash and other unwanted interfering signals. 500 1k 10k 5k 20k Specifications Power Output (RMS) 125 watts into 4 ohms; 90 watts into 80; 1 20 watts into 1 OOV AC line Frequency Response 30Hz to 30kHz (-3dB) with line output transformer (all inputs) Input Sensitivity 340mV (Aux 1 , Aux 2) 0 .5mV for balanced microphones 0.5mV for unbalanced microphones Input Impedance 50k0 for line inputs (Aux 1, Aux 2) 6000 for balanced microphones 3000 for unbalanced microphones Harmonic Distortion (0.3% from 20Hz to 20kHz Signal-to-Noise Ratio - 56dB unweighted for microphones - 72dB unweighted for line inputs Stability Unconditional The balanced outputs at pins 1 and 7 of IC1 are fed to IC2, an LF351 single op amp, to provide an unbalanced output at pin 6. This is coupled via a 2.2µ,F bipolar electrolytic capacitor to the Mic 1 gain control potentiometer, VR3. For unbalanced microphones, a 6.5mm socket with integral switch is used. This grounds the pin 3 input of IC1a, effectively converting the circuit to an unbalanced stage with only IC1b functioning. IC4, another LM833 dual op amp, and IC5 provide the balanced/unbalanced input stages for the second microphone input channel. Its output is coupled to the Mic 2 gain control potentiometer, VR5. The two stereo program sources, labelled Aux 1 and Aux 2 on the circuit diagram, are fed into a 4-way RCA phono socket. Both channels of each stereo source are mixed via 1k0 resistors to provide a mono signal which is then fed to the respective volume controls, VR6 and VR7. The signals from the wipers of VR6 and VR7 are then coupled via 0.12µ,F capacitors and 56k0 resistors to the mixer stage formed by IC1a, which is one half of another LM833 dual low noise op DECEMBER 1988 27 :I: ~ ~ n ~ O ~ I i ,.. .0056 - .,. ~ I • -II 220k 5.6pf Lf351 IC5 MIC 2 CIRCUlTRY AS ABOVE -15V I~ 1 .,. l -15V • 2.2 BP BP 2.2 I ':" MIC 2 GAINJ'":.~~ ~ VR5 ~ttf 5k LOG I __Jill __ ">-,.-,,.,,, _ *1% .0015 I •........ ...____________3.9k IC4 LM833 1eon .0015 ~~ ~ AUX 2 ■ .-.-;; I GAiii ,~ ........,,..,.. VR7 ' 50k LOG 1k R ~ ~1k Ry.,. ~1k Ly AUX 1 INPUT I SINGLE ENDED 4 301!"> * Jo';n BA~ANCED MIC 1 INPUT V---2 . 39k 3% ~ E- N- 240VAC CASE -;J,, ! L_: r----: 04 BC556 1.4V 3.9k; ~ I [__: 45.5V 22k: r---. 2.2k ~ 8 ru 120W PA AMPLIFIER I ~~ ~h~ = -r~ ~ ! -.J 3.9ki2.4V :.J seoni-:Lv 07 06 :::r ! -51V +51V r----Wh .,. 0.22I ! 16VW 22 22 16VW J)UT 0.22! SA 0.1 0.1 B 0.22+ 0.1 51V G 0 ECB 0.1 0.1 INmUT GNO ~ 16VW 22 16VW 22 IN 0 -15V GND +15V OUT ffi GND 5 S m/ VIEWED FROM BELOW ELJc 0.22+ 011 1N5404 010 1N5404\· ~ G\,JtJl.. 2s~~34 5A +51V ◄ Fig.2: the circuit features two microphone inputs (either balanced or unbalanced) and two auxiliary inputs. These signals are mixed in IC3 and fed to a power amplifier stage (Ql-Q11) which drives a 100V line transformer. amp, IC6a. The gain of this stage, for each of the two inputs, is set by the ratio of the 56k0 mixing resistors to the 220k0 feedback resistor, from pin 1 to pin 2. This gives a gain of 220/56 or approximately 4 times. Tone controls The output of the line source mixer is then fed via a 2.2k0 resistor to a feedback tone control stage built around IC6b. This is a conventional feedback tone control stage which works as follows. First, assume that bass and treble controls VRB and VR9 are electrically centred. This means that the gain for all signals is exactly unity; ie, flat across the whole audible spectrum. For the treble control, the two .0015µF capacitors in series with each side of VR9 pass only high frequencies so that bass signals are not affected by the setting of the control. Similarly, for the bass control, the .022µF capacitor in parallel with VRB bypasses the high frequencies so that they are not affected by operation of the control. So when the bass control is rotated clockwise, its wiper moves towards the input signal, which means that the feedback resistance path from pin 7 to pin 6 of IC6b is increased. This increases the gain at low frequencies and therefore boosts the bass. The same principle applies with the treble control. Note that signals from the two microphones are not passed through the tone control stage. This is normal practice in most public address amplifiers. Fig.2 shows the frequency response of the amplifier and the response of the tone controls. Main mixer Following the tone controls, the signal passes to the main mixer stage, IC3, via a 39k0 resistor. Signals to the mixer from the two microphone stages are fed via 2.2k0 resistors. Signals from the tone controls pass through IC3 with a gain of unity (ie, no gain) whereas those from the microphone stages pass through with a gain of 39kn/2.2k0 or approximately 18 times. Signals from op amp IC3 then pass directly to the master volume control, VR4. This then feeds the power amplifier via a 0.47 µF capacitor. As an optional feature we have included a mute facility on the mixer board. This can be used with microphones which have a press-totalk switch. When the mute switch S1 is closed, it kills the signal from the program source (Aux 1 or 2) and gives the microphone signal a clean background. It works as follows . Normally, Q12 is biased off by the 10k0 resistor connected from its base to the + 15V supply. Because Q12 is not conducting, Q13 has no base current and so its collector emitter impedance is high. When Sl is closed, Q12 conducts and supplies base current to Q13 . Q13 then acts as an audio switch to kill the signal at the input to the tone control stage. Note that because of the 47µF bipolar capacitor in series with the collector, no DC current flows through Q13. This is an unusual use for a transistor but it works quite effectively. In our prototype PA amplifier we - have shown transistors Q12 and Q13 on the board but we have not provided a connection to the microphone inputs. The power amplifier module is identical to that described in last month's issue, so we will not describe the circuit here. Power supply The power supply is based on that featured in last month's issue but includes the additional components needed to provide balanced ± 15V rails for the preamp and mixer stages. These additional components are mounted on·one end of the preamp board which is shown as Fig.3. The AC mains supply is passed via a 2-amp fuse and then double pole switch S2 to the primary of the 300VA toroidal power transformer :;:;:~""' _;~~~ !:.2;!-'""· ~~:-~ r~22M ~ 22µ,F 0 L _ _:~~~=-+--------' Fig.3: here's how to wire up the preamp/mixer board. Use PC stakes at all external wiring points and make sure you don't confuse the two 3-terminal regulators. Note the three wire links. (Altronics Cat. M-3092). Its two secondary windings drive a 35-amp bridge rectifier and two B000µF 63VW electrolytic capacitors to provide balanced ± 51 V supply rails for the power amplifier board. These high voltage rails also feed via 6800 5W wirewound resistors DECEMBER 1988 29 ·~ The close-up view shows the completed preamp/mixer board installed in the chassis. Notice how the two 6800 5W resistors at the bottom lefthand corner of the board are mounted end on. The metal tabs of the two 3-terminal regulators go towards the front panel. to 33V 1W zener diodes. The zeners act as pre-regulators for the 3-terminal regulators. By selecting 33V zeners with a tolerance of ± 5%, the regulators are protected against excessive input voltage; the 7815 positive regulator can withstand a maximum of + 35V while the negative 7915 regulator can withstand - 40V. The ± 15V supply rails from the 3-terminal regulators are further bypassed by a number of 22µF and O.lµF capacitors to lower the output impedance and filter out any hash. The 33V 1W zeners should be 5% tolerance. The two 6800 5W wirewound resistors are stood on end, as shown in the photos. You will need 40 PC pins for all the connections from the mixer board to external components such as the potentiometers. When the mixer board is assembled put it aside and start work on the amplifier module. The wiring layout of Mosfet amplifiers is very critical so the printed board is a crucial feature of the design. The printed board measures 163 x 95mm and is coded SC 01111881. As published last month, the board was mounted on a large diecast heatsink with integral rightangle bracket. As used in this PA amplifier it is mounted on one of the side heatsinks with. a heavy gauge aluminium angle bracket. Assembly of · the board is a straightforward matter but it should not be hurried. First, you should closely inspect the board to see if there are any shorted tracks or open circuits in the copper pat- Construction As noted above, we built the new public address amplifier into a rack mounting case. The one used in our prototype amplifier was supplied by Altronics Distributors Pty Ltd who also are the source for the toroidal power transformer and line output transformer. The mixer and preamplifier circuitry is mounted on a printed circuit board measuring 259 x 78mm and coded SCO 1112881. Assembly of the mixer board is quite straightforward (see Fig.3). Take care to ensure that the integrated circuits, electrolytic capacitors and diodes are all installed the right way around. Watch the regulators too and don't swap them around inadvertently, otherwise they'll blow. 30 SILICON CHIP The two input transistors (Ql & Q2) on the power amplifier PCB must be glued together using super-glue. This is done is minimise temperature drift of the DC output voltage. Fig.4: here's how to install the parts on the power amplifier board. Keep the component leads short and make sure that the Mosfet output transistors (Q8-Q11) are electrically isolated from the heatsink. The 2200 resistors shown dotted are mounted on the copper side of the board. -SCREWS Two layers of wire are wound on so that the start is at one side and the finish is at the other side of the bobbin. Bend the start and finish leads at 90° and scrape off the enamel coating before soldering the choke to the board. Heatsink assembly 0 0 PCB I -1 SHAKE-PROOF · - - • - W ASHERS ~• ~-NUTS Fig.5: this diagram shows how the Mosfet output transistors are mounted on the heatsink. Use your multimeter to check for shorts between the case and heatsink after each transistor is mounted. The nuts should be soldered to the PC pattern after assembly to ensure reliable contact. tern. These should be fixed before proceeding further. The PCB component diagram is shown in Fig.4. Fit the small components first, such as the resistors and diodes. Make sure that you don't confuse the small diodes (1N914s) with the 11 V zeners. The fuse clips, trimpots and small transistors can be mounted next. Qt and QZ should be mounted so that their flat faces · are touching. When you have soldered them in place, put a drop of super-glue between them and squeeze them together. The 4.3µH choke at the output of the amplifier is wound with 19.5 turns of 0.8mm enamelled copper wire on an 11mm plastic bobbin. The four Mosfet power transistors are mounted on a 4mm thick extruded aluminium heatsink bracket but with their leads passing through and soldered to the printed board. The assembly is as shown in Fig.5. We used 5mm fibreglass tubing for the insulating bushes. Smear all the mounting surfaces of the Mosfets and the heatsink with heatsink compound before assembly. The transistors are fastened to the heatsink bracket using 12mm 6BA screws and nuts. Solder the nuts to the PCB pattern after assembly to ensure reliable contact. Alternatively, if the nuts are nickel plated or stainless steel, use lockwashers. As each transistor is mounted, use your multimeter (set to a low "ohms" range) to check that its case is insulated from the heatsink. After the nuts have been tightened and soldered, the gate and DECEMBER1988 31 PARTS LIST Power Amplifier Module 1 PCB, code SC01111881, 95 x 163mm 1 aluminium angle bracket, 4mm thick, 32mm wide, 170mm long, drilled for four T0-3 power transistors and to match the PC board 4 3AG fuseclips 2 5A 3AG fuses 6 PC pins 1 plastic coil bobbin, 12mm diameter x 11 mm long; Siemens B65672-B-T1 or equivalent (or 4.3µH aircored choke; see text) 4 T0-3 transistor mounting kits Semiconductors 2 2SK 1 34 Mosfet transistors 2 2SJ49 Mosfet transistors 4 BC556 PNP silicon transistors 1 BC548 NPN silicon transistor 1 BF4 70 PNP silicon transistor 1 BF469 NPN silicon transistor 9 1 N4148, 1 N914 small signal diodes 2 11V 400mW or 1W zener diodes 2 1 N5404 3A silicon diodes Capacitors 1 22µF 16VW PC electroyltic 1 0.47µF 16VW PC electrolytic 1 0.27µF metallised polyester (greencap) 4 0.22µ,F metallised polyester (greencap) 1 .001 µF metallised polyester 1 39pF ceramic Resistors (0.25W, 5%) 1 x 27k0, 3 X 22k0, 2 x 18k0 0.5W, 2 X 3.9k0, 2 X 2.2k0, 1 x 1kQ, 1 X 6800, 4 X 2200, 2 X 680, 3 x 120 1 W, 1 x 5000 trimAOt (Bourns Cermet horizontal source leads of the Mosfets can be soldered to the PCB pattern. The four gate resistors are then soldered in place, on the copper pattern side of the PC board. Now closely inspect all your work for correct assembly and soldering. Make sure there are no blobs of solder bridging out tracks. As a 32 SILICON CHIP mount, 0.2 x 0.4-inch), 1 x 2000 trimpot (Bourns Cermet horizontal mount) 1 4 7 µ,F bipolar electrolytic capacitor 4 1 on 0.25W resistors Mixer Board Hardware & Power Supply 1 PCB, code SC01112881, 259 x 78mm 40 PC pins Semiconductors 3 LM833 dual low noise op amps 3 LF351, TL071 Fet-input op amps 2 33V 5% 1 W zener diodes 1 7815 15V positive regulator 1 7915 15V negative regulator Capacitors 2 220µF 35VW PC electrolytics 4 22µF 16VW PC electrolytics 2 2 .2µF bipolar PC electrolytics 2 0 .12µF metallised polyester (greencap) 6 0. 1µF ceramics or green caps 1 .022µF greencap 4 .0056µF greencap 6 .0015µF greencap 1 33pF ceramic 1 5.6pF ceramic Resistors (0.25W, 5%) 1 x 220k0, 2 x 56k0, 2 X 39k0, 2 X 27k0, 1 x 18k0, 2 X 12k0, 4 X 6.8k0 1 %, 4 X 3.9k0 1 %, 4 X 2.2k0 1 %, 3 x 2.2k0, 4 x 1 kO, 2 x 6800 5W wirewound, 4 x 3010 1 % , 2 X 1 800 1 % Potentiometers 2 1OOkO linear potentiometers 2 50k0 log potentiometers 1 1 OkO log potentiometer 2 5k0 log potentiometers Optional mute facility 1 BC558 PNP transistor 1 BC548 NPN transistor final check on your work, connect your multimeter (set to a low "ohms" range) and test for shorts between the supply rails and the OV rail. There is a trap here - flyback diodes DlO and Dl 1 will show a low resistance for one connection of the multimeter and a high resistance for the reverse connection. 1 3-unit rack mounting case with extruded aluminium side panels, Altronics Cat. H-0418 1 300VA power transformer, 70V centre-tapped, Altronics Cat. M-3092 1 160VA 1 OOV line transformer, Altronics Cat. M-1124 2 3-pin XLR chassis mounting sockets 2 6.5mm mono jack sockets, chassis insulated, with changeover switch 1 4-way RCA phone socket panel 1 red binding post terminal 1 black binding post terminal 1 3-core mains power flex with moulded 3-pin plug 1 cordgrip grommet to suit power flex 1 4-way insulated barrier terminal block 2 solder lugs 1 35-amp bridge rectifier, Altronics Cat. FB-3504 2 8000µ,F 63VW electrolytic capacitors 1 3AG 2A fuse and chassis mounting fuseholder 1 neon illuminated DPDT 240VAC-rated rocker switch 6 20mm black anodised aluminium knobs 1 40mm black anodised aluminium knob 4 plastic PCB supports Miscellaneous Twin-shielded cable, figure-8 shielded audio cable, hookup wire, solder, heatsink compound, screws, nuts, washers. With the power amplifier module complete, carefully check your work for misplaced parts and faulty soldering. Do not apply power at this stage. Next month, we will show you how to assemble the two modules and the power supply in a rackmounting case. ~ _ _ _G_E_T_C_H_A_R_G_E_D_U_P_ _--r-N - IC_A_D_BA_TT _E _R_Y_CH_A_RG_E_ RS~ I THIS CHRISTMAS jl, I "AA" Nl:~!~!'HICAD. BATTER~~~$2.95ea (rechargeable up to 600 times) "AA" ARLEC 500mAH. . ..... NOW $8.95pr (rechargeable up to 1000 times) ' "AAA" ARLEC 180mAH. . .... . ... NOW $9.95pr (rechargeable up to 1000 times) o( ~ ~ "C" size ARLEC 1.2AH. . ......... NOW $16.95pr (rechargeable up to 1000 times) "D" size ARLEC 1.2AH. . ..... NOW $17.95pr (rechargeable up to 1000 times) 9 volt VARTA 100mAH. . .......... NOW $17.00ea (rechargeable up to 1000 times) 6 volt LANTERN RECHARGEABLE • 6 vo lt <at> 5000mAH • Complete with charger for 240 volt & 1 2 volt operation ONLY s59.95 • BATTERY AVAILABLE SEPARATELY oNLY s29.95 "UNIVERSAL BATTERY e )ooG • ;,":i:,;~,A•RJ!A'!n.~ScT~~••' '''°" ~.~ 29 •~ • LED charge indicators • Voltage level meter ONLY $ "ARLEC" NICAD CHARGER "Designed for these remote control cars" • Do up to 8 x "AA" and 2 x 9volt cells • 2 year guarantee .95 Use your rear window demister as a car radio antenna Fed up with replacing your car's radio antenna? Your rear window demister can be adapted to do the job instead. By JOHN CLARKE & GREG SWAIN Let's face it - car radio antennas usually don't last very long. They can suffer a variety of fates. They can get gunked up with dust and grime and go open circuit; they can be bent by some mindless moron; or they can be damaged by overhanging branches in your driveway. If you have a power antenna, it's usually not too long before the nylon gears or the clutch in the drive mechanism wear out and the antenna jams. When that happens, the 34 SILICON CHIP antenna is then virtually useless. At around thirty bucks a hit (or more), replacement power antennas are not exactly cheap. This project is designed to solve your car radio antenna hassles once and for all. It's a simple adaptor circuit that lets your rear window demister function as an efficient antenna. In fact, this scheme will work much more efficiently than the traditional coat hanger antenna replacement. And because the demister element is attached to the inside of the rear window it's vandal-proof, weather-proof and never needs replacing. How it works Unfortunately, it's not simply a matter of just clipping the antenna lead to one of the demister terininals. That would be too easy. There are two problems. First, we have to isolate the demister element from the supply lines at RF (radio frequencies). If we don't do this, any RF signals that are picked up by the demister will be shunted to ground via the battery. Second, we have to keep any high frequency noise that's present on the supply lines out of the demister circuit, while still allowing the heater current to flow. In an auto PARTS LIST L1,L2 : 30T, 1.25mm ENAMELLED COPPER WIRE, BIFILAR WOUND ON A NEOSID 28-042-31 F14 FERRITE RING CAR ANTENNA ADAPTOR Fig.I: the circuit is basically a simple LC filter which is interposed between the supply lines and the demister element. Ll and L2 are wound on a large ferrite ring core. electrical system, high frequency noise is always present on the supply lines. It is caused by the ignition system, by switching transients and by the operation of electrical motors and .relay contacts. This electrical noise must be kept out of the antenna circuit otherwise it will cause audible interference to the reception. Fig.1 shows how this is done. The circuit employs a simple yet very ef- · fective LC filter arrangement which is interposed between the supply lines and the demister element. Both supply lines are first decoupled using 0.22µF filter capacitors and then fed to the demister element via inductors L1 and L2 which provide further filtering. As a result, any high frequency noise on the supply lines is filtered out before it reaches the demister element. Ll and 12 also provide RF isolation of the demister circuit from the supply lines. These two inductors are wound on a large ferrite ring Three wire straps spaced at 120° intervals are used to secure the toroid core to the PCB. Note that the toroid is bifilar wound (ie, the two windings are wound on together). Use shakeproof washers under all nuts. 1 PCB, code SC05-1-1188-1, 72 x 85mm 1 aluminium case, 135 x 75 x 55mm 1 Neosid 28-042-31 F14 ferrite ring core 3 0.22µF ceramic capacitors 1 .01 µF ceramic capacitor 1 1 80pF ceramic capacitor 3 metres heavy duty coaxial cable (eg 7 50 TV antenna cable) 6 metres light duty coaxial cable (for antenna lead) 3 metres 1.25mm enamelled copper wire 2 500mm lengths of heavy duty hookup wire 4 solder lugs 4 5mm ID rubber grommets 4 9mm standoffs 1 car radio antenna plug Miscellaneous Screws, nuts, shakeproof washers, automotive spade clips. and provide about lkO isolation between the supply and demister element at AM frequencies and about lOOkO isolation at FM frequencies. Note that quite a large ferrite ring has been specified (25mm ID) for this circuit. This is to prevent core saturation due to the high current that flows when the demister is turned on. The RF output is taken from one side of the demister circuit and coupled to the antenna lead via a .OlµF capacitor. This capacitor is necessary to isolate the + 12V supply from the antenna input. The 180pF capacitor to ground on the negative side of the demister has an impedance of about 9000 for AM signals but only a few ohms for FM frequencies. This means that, as far AM signals are concerned, the demister element functions as a short wire antenna (ie, short relative to the wavelength of broadcast AM frequencies). Note: the wavelength of a 1MHz radio signal is 300 metres. At FM frequencies, the negative side of the demister element is virtually shorted to chassis. The demister element now functions as a horizontal whip antenna which is DECEMBER 1988 35 TO DEMISTER ~ ~ L1 y L2~ Fig.2: here's how to wire up the Car Antenna Adaptor. The ferrite ring is bifilar wound using 30 turns of 1.25mm enamelled copper wire (see text). Use 750 TV cable for the demister connections. longer than the optimum 1/4wavelength but still functions quite well. Construction The car antenna adaptor is built on a PCB coded SC05111881 and measuring 72 x 85mm. This is housed in an aluminium case measuring 134 x 75 x 55mm. The inductor is wound using heavy gauge (1.25mm] enamelled copper wire (ECW). Because the current flowing through the supply wires to the demister element is quite high, the windings must be I .. The antenna and demister leads enter the case through rubber grommets. Note how the shields are terminated on solder lugs. 36 SILICON CHIP wound so that the flux created by one wire is cancelled by the flux from the return wire. This cancellation is achieved by winding both wires together and by ensuring that the current in each wire flows in the opposite direction to the other. To wind the toroid, take 3 metres of 1.25mm enamelled copper wire and fold in half to give two parallel lengths of 1.5 metres. They should then be twisted using a hand drill until there is one twist about every 5mm. Now wind 30 turns through the toroid. The wire should be wound on tightly with each winding close to the preceding winding. There should be a gap of exposed toroid between the ends of the windings for about 20° of the radius. The toroid is secured to the PCB using three tinned copper wire straps. Clean and tin the ends of the leads before mounting the toroid and make sure that you don't transpose the ends of the L1 and L2 windings. You can separate the two windings by using your multimeter to check for continuity. After the toroid has been installed, you can solder in the five capacitors. The PCB can then be positioned in the bottom of the case and the four corner mounting holes marked out and drilled. You will also have to drill holes in the sides of the case to accept the cord entry grommets and to mount the solder lugs. Fig.2 shows the details. The wiring from the PCB to the demister element should be run using shielded 750 TV cable. This should have a solid 1.25mm central core so that the cable can carry the demister current. The shields are soldered to the solder lugs mounted on the case as shown on Fig.2. Do not use unshielded cable for these connections otherwise you will get interference problems. The antenna lead can be run using 500 coaxial cable (eg, RG58C-U]. Make the cable long enough to reach from the rear parcel shelf to the radio and terminate the free end with an antenna plug. Antenna plugs are readily available from kitset suppliers. Once the wiring has been corn- Getting at the antenna socket can be difficult on some cars but not on the Holden Commodore. All you have to do is remove the ashtray. On other cars, you can gain access to the socket by removing the glovebox. Do not touch the spade clip connections to the demister. If they break away from the windscreen, they will be difficult to repair. DEMISTER pleted, the PCB can be mounted in the case on 9mm standoffs and secured using machine screws and nuts. Installation The Car Antenna Adaptor is best mounted beneath the rear parcel shelf in the boot, near to the power wiring to the demister element. On most cars, you will find two short wires running up to the demister terminals from the rear parcel shelf. The leads are usually plugged into spade connectors which are attached directly to the windscreen. Do not interfere with these spade clip connections. If you do, you A conventional antenna plug is fitted to the end of the antenna cable. This then plugs directly into the radio's antenna socket. could pull one of the terminals away from the windscreen and damage the demister element. And that would not be an easy repair job. Instead, we suggest that you break the power leads under the rear parcel shelf and interpose the Car Antenna Adaptor there. You may even find that the power leads to the demister are conveniently connected to the rest of the car's wiring via bullet connectors or a plug and socket arrangement. Fig.3, shows the wiring details. The most difficult part of the installation will be running the shielded antenna lead to the front of the vehicle. In most cars, you will be able to hide the lead by running it along the floor under the door trims. From there, the lead can be run behind one of the kick panels to the underside of the dashboard. After that, it's simply(!) a matter of plugging the lead into the antenna lead from the radio (easier said than done on most cars). A little ingenuity often helps here. For example, on some cars you can gain access to the antenna socket by removing the glovebox or by pulling out the ashtray (eg, on the Holden Commodore). In difficult cases, it may even be r ___ SHIELDED CABLEli , RAOIO--SHI-EL-DE.... D_ _ _,.. ANTENNA LEAD DEMISTER ANTENNA TO SWITCHED DEMISTEh WIRING CHASSIS TO CHASSIS OR NEGATIVE DEMISTER WIRE Fig.3: how to wire the adaptor circuit to the demister element. The unit is best mounted under the rear parcel shelf. necessary to remove the radio. A workshop manual will show you how to go about this job. When all is complete, the installation should be tested with the motor running to check for interference. You should also try turning the demister on and off to make sure it still works in its original role. As a final step, if your car radio has an external trimmer for AM, it should be adjusted for best reception at the top of the band. ~ DECEMBER1988 37 ,-------------------------~~...;::::,:J Why Waste Your time With Other Suppliers I Altronics Can Deliver Any Of The Quality Products . 1 To You Tomorrow - Just Phone Your Order Toll Free 1 I Jack O'Don On 008 999 007 ·I• I M/Directo~eII Country Clients Please Allow Additional 48-72 Hours I ·I I . ~------------------------------Sensational Super Buy On Quality Sampson 12V Recharg a I Batteries This Quality 12V 1.2AH Lead Acid Battery Sells Elsewhere for $30! Altronlcs Price? i:199.oo Just $15 ltr■ H gh P er Capacity Polypr PY e e ••• Driver• f,) This brilliant little mixing console is absolutely packed with features. () Allows blending of Microphone. two Phono inputs and either two Tape or {) Turner inputs • Right and left VU meters • Separate Bass and Treble /(co ntrols • 5 slide level controls • Fader control between Pho no pick ups for / i i professional c ueing • Headphone monitor switch • Talkover facility . Save 25% Thi• Month )\ SPECIFICATIONS: 12" (300mm) Model • Input Mic 0.5mV 600 Ohms Phono 3mV 50K Ohms Tape/Tuner 150mV 100K Ohms • Output 250mV •Frequency Re ■ ponae 20Hz to 20Hz (plus or minus 1db ) • Tone Control (Treble) 10KHz (plus or minus 12db) • Tone Control (B ■ -1) 100Hz (plus or minus 12db) • Ol1tortlon Less than 0.07% • ··· S/N Ratio More than 60db • Headphone Impedance 4-6 Oh:ns • Olmen1lon1 318 (L) x 217 (W) x 85 (H) 100 Watts continuous input 150 Watts intermittent input Impedance 8 Ohm Sen■ltlvlty 93db Weight 3620gm ,)) }) \) }:( -o ol C 3070 9 9 $ Normally $139 Our sophisti ca ted 'NEW' Audio Mixing Console is ideal for ':ive' recording • PA mixing • Fantastic Tape recordings • Even Stereo/ Mono VCR recording . A truly professional deck that features separate R/ L 5 band graphic equalisers• Echo and Peak LED level indicators• Talkover faci lity • Separate H/Phone level control • 'Patch switch bank • Individual microphone, Phono 1 Phone 2, Aux/Line 1, Aux/line 2, and Master slide level controls. Blend up to two magnetic or crystal turntables, two tape decks or tuners and two microphones all at once!' SPECIFIC,\TIONS: • Input Mic 1-0.SmV 600 Ohms Mic 2-0.SmV 600 Ohms Mic 2-0.SmV 600 Ohms (low imp.) 2.SmV 10K Ohms (low imp.) Phono 1 & 2 (Mag) 3mV SOK Ohms Phone 1 & 2 (Cry) 150mV 100K Ohms Tape/Tuner 1 & 2150mV 100K Ohms • Equall1er 5 frequency bands-60Hz, 250Hz, 1KHz, 4KHz, 12KHz-Boost Cut range-plus or minus 12db <at> Centre frequency. • Output 1.5V/0.775V (Selectable) • Frequency RHponH 20Hz to 20KHz plus or minus 1db • Ol1tortlon Less than 0.05% • SIN Ratio More than 50db • Headphone Impedance 4-16 Ohms• Echo B.B.D.System • Delay Time 30-200mS • Echo Repeat Control• Delay Time Control• Dlmen1lon1480 /l \ x 240 IW\ X 110 (H\ Mylar Stereo Phones ith D namIc Mic Simply brilliant Mylar Stereo headsets & dynamic mic combination. Headphone Spees. 20Hz - 20,000Hz, 32 Ohm, 102 db/uW, 3 .5mm stereo jack, 6.35mm stereo jack, adaptor. Microphone Spees. Dynamic type, 300 Ohm , 100Hz - 15,000Hz, -80 db<at> 1 KHz, 3.5mm MCo9no05ja5ck. s29.95 a11lve nfra-Red Lit Guard odllg Co How often have you thought there could be a prowler outside your door? Install a LIie Guard & (once armed) any "guest" wlll be floodllt when detected by thlI highly sensitive Intra-Red Detector. Please Note FloodlampI & Holders Not Supplied S5350 s135 The lite Guard detects a moving person or vehicle by comparing the background temperature with a rapid change of temperature across the detection beams. So when Lile Guard detects movement across the coverage area, it will turn on the floodlight(s) for 1-20 minutes aa pre-adjusted. Specification■: Detector: Dual element pyroelectric PIR sensor • Raintight outdoor all weather operation. • Photocell to deactivate sensor during daylight• Operating Voltage: 240V AC, 50Hz. Operation time: Adjustable 1-20 minutes. Ser,I1tlvlty: Adjustable 20'-50', 30 beams• Aimable desired direction with 2 ball joints• switching Capability: 500W max. ,.,.,.,,,,,,,,, i/=:=:=:=: ='?}')') ---~ ~ ; ; .. .. Just Imagine a Security/ Alarm System you can Install In about an hour- Uses no Wiring or Cables and Costs Less than $1 for the Mounting Hardware UHF 305MHz Microprocessor Controlled Wireless Security System Commercial grade, quality alarm systems are expensive-Just phone one of the "Name" security firms and get a quote for your home-our estimate is that it will be anything up to $1,000 just for the equipment - then there.Ii the ln1tallatlon -countless holes punched through walls, miles of wiring and a day or two of installers labour and thal'I around$35 per hour then day,. Hardly worth the effort It It? Alter all what have you gotto loon? - Only Iha Video Player CD Player, Camera, HI FI, TV, Jewellery and-so onll Well all that 11 now changed - with our brllllantly englnNred Home Guard Wlrele11 Security System Read On - Take It With You If You Move Apart from the flawless operation of the Home Guard System-One of the great features is its application with rented or leased premises-Lets face it, money spent on installing a wired system in your Home or Office , Factory etc . is irrevocably lost when you move on . With the Home Guard you simp ly take it with you . This alarm system is a brand new design that features completely wireless connection to all accessories, even the reed switches . Think of how easy it Ideal for the lounge room , family room or is to install a " Wireless" alarm system . The benefits are endless. e.g . arming your Flat or Townhouse with an alarm you don 't need to run hallways e.g. anywhere where an intruder is likely to pass through . Mounts up on the wall or w ires through the roof or drill great holes through your walls. When moving house the alarm is simple to dismantle and re-install elsewhere . on top of bookshelves etc . Detects movement within an area of 9M by 9M by sensing intruder The system divides protected 3reas into either perimeter zone or internal body heat movement through the protected area zone , programmable by dip switches in each transmitter/ detector. Pocket Should not false trigger with the family cat or remote control can simply arm or disarm your house perimeter from your curtain movement etc. - as is the case with the bedside when retiring etc. this allows essential protection while cancelling internal zone as desired. Each transmitter/ detector unit can be cheaper Ultraso;c ~;;~ programmed into interior or perimeter zone . Zones can be programmed for instant or delayed trip . The system has a built-in ear piercing siren for intrusion and panic alarm signals Passive Infra Red Movement Detector $ 129 ■DO Remote Plezo Siren System Is Comprised Of : This unit is an optional line carrier receive r. Receives signal through ' AC' line i.e. it would ideally be located in , say , the roof space and plugged into mains power . Main Control Receiver s 52so s125.oo Complete System Special Package Price One One One One S S S S 5265 5270 5280 5285 Main Controller Reed Switch Passive I/ R Detector Wall control un it . • Wireless reception of external or internal sensors or detectors . • Selectable home or away modes for selecting internal and external arming or just external to allow movement inside the building • Built in Piezo electric siren gives different signals to indicate different functions. • Sends signal down power line to activate one or more remote sirens . • Programmable Arm/ Disarm switch buttons. The main control receiver runs on 240V AC with a 12V 1.2AH battery for emergency backup . Al l other units with the exception of the line carrier , run on a 9V battery each . The average life expectancy is approximately one year . System works around the 305MHz frequency where there is less chance of false alarm . The range of the unit is normally 80 metres in open space . Alarm and Indication Sounds Intrusion Alarm - Panic Alarm - Arm Tone - Disarm Tone - Exit Click Tone - Monitor Tone - Tamperinq Alarm. Detector/Transmitter Unit (Reed Switch) Suitable For Windows and Doors I 11 s499 Nole: For larger installations your system may well require several Reed Features: ::!::ilil;I!i!:::1:! 1I I1Il ~ s 5260 Normally S570 Accessories = :•:._'} ,=/==::::'::: / {=:=· :·,::' =:=·=•.·......... This Month This consists of an enclosed reed switch and compact UHF transmitter and a removable enclosed magnet. The unit is at rest when .magnet and reed are side by side {within 25mm or 1 inch) . When the magnet is moved away more than approximately 1 inch the alarm signals to the Main Control Receiver and the alarm is sounded . In practise the Reed/ Transmitter is mounted on the door or window frame with the magnet on the moving door or window. s 5210 s55 .oo switches, movement detectors and 2 or more sirens . Also the remote door controller and or pocket remote controls could be very worth while accessories. The fantastic thing about the Altronic system is you simply add more detectors as you discover the need - no wiring, no e:(pensive technicians , no modifications to equipment . Hand Held Control Transmitter Unit A real joy to use - keep it at the bedside table allows you to, say , arm the house perimeters when retiring or you can take it with you when you go out , arming your system after you loc k the door. Unit is a funct ion control transm itter to send 4 different signals. Off - To disarm the system before entering . Home - To instantly arm the system with 'Perimeter' detection only . Away - To arm complete system after a given exit delay time of about 40 seconds. Panic - To start an emergency signal whenever needed, in any mode. s 5215 I I s59 .DO Front Door Keypad Control un·t This handy accessory virtually duplicates the function of the Master Controller unit but at a more convenient location i.e. just inside your entry ·door etc . System can thus be armed or disarmed without the need to go to Master unit. Especially handy for larger homes or offices. s 5285 s99 .oo, ~ ~ : : : ~ - ~-:;l;;~; Ja~k/ ~~~~t~~ell !~ ~;~ ~ ~ ; ; Great Kit Projects To Build Many Just Released Brllllant Performance Stereo Pre Amp Go anywhere 240V Mains · Power fr.om your car or truck battery with these fantastic DC to AC Inverters Studio 200 Stereo Control Unit (Slllcon Chip June/July'88) Out-Performs Commercial Units Costing $600 Plus The Studio 200 Stereo Control Unit is companion to the studio 200 stereo power amplifier (or other power amps) . It features slim single unit rackmount profile, treble, bass, balance, inpu_t selector, tape monitor switch, stereo/ mono switch and volume control. Inputs include phono, tuner, CD , VCR and tape loop. Power House 600W Inverter (See EA Dec'87) A must for farming, camping , mining, boat ing, remote settlements and wherever else 240V power isn 't available. Feature■ : Strong custom steel chassis• Industrial grade power coat finish• Can be configured to operate off either 12Vand 24V DC• Very little internal wiring • Manual or Auto start facilities • Low battery cut ou t • Compact Toroid transformer. Fully Built & Te■ted K 6770 KIT VERSION Calling All Audio Purists This Great New Amp From Silicon Chip Is For You Studio 200 Serles 100 Watts Per Channel Power Ampllfler K 5010 s399 Features: • In-Built speaker protection• Toroidal Transformer (low hum} • Black Satin Finish• Low leakage power supply capacitors • Housed in Rugged Custom Chassis. Specifications:• Output Power 100W into 8 Ohms Freq. Res.(at 1W) 20Hz-50KHz + or - 1db Input Sensitivity 870mV Harmonic Distortion (20Hz-20KHz) 0.1% Signal To Noise Ratio 100db or Better Protection 5A fuses plus RDE245A Polyswitch Damping Factor (without Polyswitches) 100 (with Polyswitches) 100. Stablllty Unconditional. K 6774 12V INPUT K 6775 24V INPUT s425 s525 s525 300 Watt Inverter With Auto Start Operates From 12V Car Battery Features: Auto start draws power from your battery only when appliance is plugged in and "turned on" i.e. battery can be left permanently connected if required. • Voltage regulated • Current Regulated • Current Overload unit self limits - Single PC Board construction - easy to build as there is very little internal wiring . Complete Kit K 6750 Dlscolite (See SIiicon. Chip July/ Aug'SS) Add Some Colour To Your Next Party s>·•5;;~:.:·· s279.oo ,.,,,,., :,-i•• ••'u " ' "" The Discolite Flashes party lights on and off in beat with music from your amplifier. • 4 light channels controlled by 4 separate audio channels • Forward, reverse and auto-reversing chaser patterns• Simultaneous strobe on all four channels • ' Alternatirig light patterns • Music modulation available on chaser, strobe & alternate patterns• Inbuilt microphone for beat triggering or audio modulation of lights• Direct inputs for beat triggering or audio modulation of lights • Sensitivity control • presettable sensitivity levels for each channel • Front panel LEDs mimic light display. Great For Parties, Shop displays and special lighting effects. Transistor FET Zener Tester (See EA Feb/Mar'SS) s49 .95 New updated circuit incorporates facilities for testing transistor FETs and Zeners etc. Features: • Gain • Leakage • Breakdown Voltages • Zener Voltage • Polarity - NPN/PNP :~ . _.;:.:;. . ;~;••----•:::::::::::llll1::::::llll1:: : ■lllllll1:::::::;:[~'.:J- K 2527 Low-Cost Unit Checks Values from 1pF -100uF Upgraded Digital Capacitance Meter The readout consists of a bright 4-digit LED display and the ful l sca le readings for each range are 9999.9nF and 99.99uF. No adjustments are necessary when taking a reading. You simply connect the capacitor to the test terminals and select the appropriate range . The circuit can accurately measure capacitance down to one picofarad (1 pF). This is made possible by the internal null i ng circuit which cancels any stray capacitance between the test terminals or test leads . So when you measure a SpF capacitor, the unit will display SpF. save$$$ 1 1t,e co• ol\ "'erc\al ol co"',~alel\ltl Super Low Price on Famous EA 8 Sector Alarm System Kit (See EA Mag,Jan '85) eQII • Fe ■ ture1: • Alarm has 8 separate input circuits - 8 sectors can be monitored independently. • Each input circuit is provided with an indicator LED and a sector On/ Off switch . " Individual sector isolation allows the user to have some areas of the premises habited while others remain protected e.g . Inside Off/ Outside On. • Inputs accept both normal ly closed and normally open sensors. • Two inputs provided with an entry delay between 10-75 seconds). Internal trip warning buuer-alerts owner/ occupant of pending alarm operationgreat for the " forgetful " amoungst us . This buzzer is pre-settable between 5 and 55 seconds prior to Alarm. • Unique circuit detects automatically when any N/0 or N/C loops are either open circuit or dead short. e.g. oomeone trying to brtdge Bench Top Power Supply 3-30V to 1 amp Max.with variable current llmlt FEATURES: * Output 3 to 30V at 1A ~ Short cir cuit protected• Load switching• Current limiting . Dual scale meter • Housed 1n our Delu xe " ABS " instrument case SPECIFICATIONS: -. Ou t put Voltage - 3 to 30V -. Outp ut Curren t - 0 to 1 amp (fully variable ) • Load Regu lation• Better than 0 .2% from Ot o full KIT K 3210 load-. Output Ripple-Less than 2mV RMS reed 1wltche1 etc. • Switched output can be used to send a si lent alarm through an auto-dialler circuit or similar. S 5065 KIT (without Back Up Battery) (12V 1.2AH Backup Battery) Now Only $15.00 Converter 24V To 12V DC (Slllcon Chip Dec'87) Laboratory Power Supply Enables 12V appliances like stereos, 2 way radios, CB's etc. to operate from a 24V battery. • Operates from 18V- 30V. Output is 13.6V at 5 amps. K ~~1s s59 .00 mn 174 Roe St. Perth WA 6000 PHONE TOLL FREE 008 999 007 Perth Metro & Alter Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 AL TRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. PIH •• Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don't forget our Expre11 Mall and Phone Order Service - for the coot of• local call, Bankcard, Yiu or Mutercard holder• can phone order for ume day deopatch. K3300 3-5 Voll• at up lo 5 Amp■ $ 195 Designed by Electronics Australia , this supply has been one of our most popular kits. Our version incorporates refinements and 1s now housed m an attractive , tough " ABS" instrument case. This all new compact version has been made possible by the use of a highefficiency Toroid Power Transformer. So you win four ways - less heat, less weight - Greatly enhanced appearance and easier to build Remember the Altronlc1 Kit 11 fully drilled and punched. Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) Colin Fobister 437 4077' Perth 09 328 2199 STAN DARO DELIVERY & PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 7 days from day you post order to when you receive goods $7.00 OVERNIGHT JETSERVICE - We process your order the day received and despatch via. Overnight JelHrvlce Courter for delivery next day Country areas please allow additional 24-48 hours. Weight limit 3Kgs (3Kgs covers 95% of Orders). $10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDER - Bankcard.Visa, Mastercard Holders can phone order tol l free up to 6pm Eastern Standard Time. Remember with our OvernlghtJelMrvlce we deliver next day. WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K.B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARR.ATHA Daves Oacitronic 854836 MANDURAH Lance Rock Retravision 351246 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronic ■ 521713 Farmer Electronic ■ 522987 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOURNE Winscott Trading 6995740 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truacott Electronics ■ -7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411 4 11 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 SA CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIE& BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 COUNTRY MT.GAMBIER South East Electronics 250034 WHY.ALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 CAAINGHAH Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218 COUNTRY COFFS HARBOUR Coffs Habour . Electronics 525684 ° . · NELSON BAY Nelson Bay Electronics 813885 NEWCASTLE Novocutrlan Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 _ B_lue R_lbbon Deal~ro are highl ighted with a ■. These De_alers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. Because standard insulating bushes were used, the heatsink bracket was spaced off the board. The bracket should sit right down on the board . The required insulating sleeves for the heatsink assembly can be made by cutting off the washer portion of the insulating bushes using a utility knife. • • IDIC • Kit Clinic is an occasional feature which takes a look at readers' problems with SILICON CIDP projects. It is published to help other readers who may experience similar problems with the same projects. Dear SILICON CHIP, I have built three 100 watt power modules as described in the December 1987 issue of SILICON CHIP. All three modules are gutless; they don't deliver any power to speak of. I've noted that the power transistors don't get hot but the protection thermistor does get very hot; this when attempting to drive the modules to full power. Otherwise, the amp modules seem to working OK. • When we had a look at one of this reader's amp modules we were reasonably encouraged. Superficially, it was quite well constructed although not to the letter of the article; there were a number of specific deviations. These were as follows. 42 SILICON CHIP First, the assembly of the power transistors and heatsink bracket onto the printed board wasn't right. Instead of the heatsink bracket being flush down onto the printed board, it was spaced up by about 1mm. This was because the reader had used standard insulating bushes instead of the insulating sleeves specified in our heatsink assembly diagram. He could have made the required sleeves by cutting the washer portion off the insulating bushes. (Our photo shows how you can do this with a utility knife). We also found that none of the screws retaining the power transistors and heatsink bracket were tight. One screw was decidedly loose and there was a noticeable gap between the heatsink mounting surface and the bracket. The heatsink screws need to be tight otherwise the heat transfer from the transistors will be poor and they will overheat. Fixing this problem was not simply a matter of tightening the screws because the base and emitter leads were soldered to be board. Tightening the screws would either bend the board or the transistor mounting flanges. Inevitably, the latter happened. To correct the problem properly, we had to desolder the base and emitter leads of all four power transistors, tighten the screws and then resolder the transistor leads. We did not bother to correct the heatsink bracket assembly - time is a problem at SILICON CHIP. Solder connections We then checked all the soldering on the board very carefully. A number of the solder connections were suspect because the component leads were not properly tinn- Don't leave the small signal transistors at full lead length. Push them down close to the hoard so that they cannot be bent over and their leads shorted. ed. This did not mean that the components concerned were not connected into circuit. At some time in the future though, these connections probably would have played up. Having checked all the soldering we connected a power supply ( ± 40V DC) and checked voltages in the circuit. Everything seemed to be OK except that the quiescent current (the current drawn by the amplifier when no signal is present) seemed to be too low (less than 10 milliamps). This was checked by connecting a digital multimeter between the emitters of Q12 and Q13. The measured voltage was flicking between 1 and 2mV DC. Using Ohm's Law, we divided 2mV by 0.440 (the total resistance between the emitters of Ql 2 and Q13) to get a calculated current of 4.5mA. Allowing for the fact that a similar current should be flowing through Q 10 and Q 11, the total current would have been less than 10 milliamps. Accordingly, we tweaked trimpot VRl to obtain a voltage of 11mV DC between the emitters of Q12 and Q13. We checked that the voltage between the emitters of Q10 and Ql 1 was very similar. We could have checked the quiescent current by the procedure set out in the original article, using 5600 resistors across the fuseholders. We used to quick method to save time. The RDE245A thermistor (left) must he used with the high-power module. It is about 20mm in diameter and blue in colour. Do not use the smaller RDE115. Now we could proceed to a the published spec. All that was power check. The unit was con- needed was the correct PTC nected to a dummy load resistor of thermistor. By the way, the RDE 115 ther80, with a rating of several hundred watts. We then fed in signal mistor is about 11mm in diameter and watched the output on an and yellow in colour. The RDE245A oscilloscope. Sure enough, the unit thermistor is much larger; 20mm in was not delivering the full quid diameter and blue in colour. It can only a few hundred milliwatts in be clearly seen on the cover of the fact. December 1987 issue. We then touched the PTC protection thermistor and yep, it was Other comments stinking hot. This was because the We noted that the small signal thermistor was high in resistance . . transistors were installed with It was in "protective" mode. Then their full lead length. We prefer to the penny dropped. It was the see these transistors pushed down wrong PTC thermistor for this into the board and soldered so that amplifier module. their lead length is no longer than The reader had built the high- about 5mm or so. This makes them power version with four output much more rigidly mounted. When transistors but had used the RDE they are installed with long leads, 155 thermistor intended for the they can be bent over so that their lower power module which is leads short and thus cause the designed to deliver 50 watts into amplifier to malfunction. 40. For this higher power module Interestingly, if the thermistor the correct PTC thermistor is the had been the correct type, the RDE 245A. module would have been able to To check that the module could deliver the full power. If it had been deliver the full output we just driven to full power though, shorted out the thermistor. Now we chances are that one or more of the were able to get just on 50 watts in- power transistors would have to 80 or 100 watts into 40. Har- seriously overheated and perhaps monic distortion at mid frequencies blown. and medium power outputs was It also seemed that the supplied less than .01 %, depending on how thermistor was now "tripping" the leads connecting to the module prematurely. Whether it had were arranged. become faulty because of long and As far as we were concerned repeated efforts to get the amplifier then, the module was well within to do its stuff we cannot say. .~ DECEMBER 1988 43 THE WAY I SEE IT By NEVILLE WILLIAMS Would you please pass the salt? I need a few grains! If there's any truth in the old saying about accepting dubious propositions "with a grain of salt", some of the statements that have been bandied around recently in the context of video and audio are surely calculated to increase considerably one's intake of sodium chloride! First up, there's the dicey business of moving TV channels into the UHF band. In fact, this rather cantankerous heading and introduction was triggered by yet another discourse from TV presenter Bill Collins, on the subject of computer coloured films. The same theme has been repeated so many times in so many places that it's difficult to treat it as seriously as some would apparently wish. But more about that later. Even before I had time to put finger to keyboard, that particular topic was overtaken by an unexpected update from the Illawarra area, along the southern NSW coastline, where broadcasters, service organisations and viewers are currently in the throes of changing over to an all-UHF system of TV broadcasting. (This same area provided the setting for the "Serviceman's Log" in October last and the accompanying map may be of assistance to interstate readers). I discussed the reasons for the changeover in the May issue of SILICON CHIP, under the heading: "Is UHF TV Really as Good as it's Cracked Up to Be?" A follow-up item "The Switch to UHF TV on the 44 SILICON CHIP NSW South Coast" appeared on page 37 of the October issue. Most readers should still have the articles on hand so I will resist the temptation to re-state their contents. In both articles, I expressed misgivings about official attitudes and the possible implications for some viewers currently dependent on the VHF transmissions. Hence the heading on the May article, as above, and the reservation expressed on page 17: "How reception will compare across the total community remains to be seen. I'd be surprised if there weren't plenty of complaints over the first few months". The problems take shape That observation is already looking like an understatement. Since it was written there has been rising apprehension among those who are actually coming to grips with UHF TV in the area, culminating in what have been dismissed by some as "alarmist" statements locally and in the regional press. When brought to my notice, I could think of no better person to contact than Jim Yalden (VK2YGY), a TV serviceman who works in the area. Not only is he actively involved and well informed about the local scene but his practical experience dates back to a lengthy stint in the UK, when UHF colour television was being established there around 1970. Having acknowledged that some of the stories doing the rounds were "alarmist", Jim went on to describe a situation that, itself, seemed to me to be nothing short of alarming for some viewers at least! Since I first discussed the matter with him, earlier in the year, he and his fellow servicemen have been busily installing UHF antennas in the Illawarra area and observing at first hand reception from the three main UHF transmitters on Knight's Hill, near Wollongong, all currently operating at full power. As I write, the antenna(s) have yet to be reinstalled on a somewhat taller mast on the same site but the results so far have been anything but encouraging. The additional height may help but then again, it may not. Recently, an engineer from a major Sydney TV station mentioned to me a situation that he'd come across in a middle east country. Having installed the antenna on a lofty tower dominating the flat desert-like countryside, engineers expected the signals to " go on forever". Instead, the coverage was described as "pathetic". The situation improved dramatically, however, when the antenna was lowered from 300 metres to less than half that figure. Fig.1: this map shows the area affected by the changeover to UHF. Despite high power, shadowing and severe fading are causing problems. The problem was apparently due to atmospheric ducting and while it involved VHF signals in that instance, something similar could conceivably affect UHF transmissions. Limited coverage & fading As matters stand on the NSW South Coast, the UHF signals are proving to be noticeably less accessible in remote or shadowed areas than the existing VHF service and that alone may affect a lot of viewers. No less disturbing is the fact that the UHF signals appear to be subject to periodic fading, presumably due to fluctuating atmospheric conditions over the relatively long signal paths involved. The fading is much more noticeable than was encountered by Jim Yalden in the UK, or by one of his fell ow servicemen in Canada and the USA. Time and again, Jim said, installers have measured · the field strength at a customer's home, before erecting a UHF antenna. When they've returned later with the hardware, they've been faced with a totally different reading. At Jim's own home, about 80km from the Knight's Hill transmitters but otherwise well sited, he receives a relatively good picture, at a signal strength that averages about 800 microvolts. But it swings periodically through a range of about 6dB. For other viewers, in poorer locations or further out, the fading spells the difference between "watchable" signals and periodic complete "blank screen" drop outs! A proposition, accepted in the area, is that planning has proceeded on the broad - but technically dubious - assumption that, given a substantial increase in ERP (effective radiated power), the reach of similarly sited UHF transmitters should roughly approximate that of their VHF counterparts. Accordingly, the new ABC UHF transmitter is rated at 600kW and the commercial WIN-4 at the maximum permissible lO00kW; this compared with the 100kW limit for VHF. But things aren't working out that way in practice because of manifestly different UHF propagation characteristics, the unexpectedly severe fading effects and the fact that comparable field strength is not good enough. At UHF, typical domestic receivers require a larger signal to ensure a clean picture, around 500µ V rather than 200µV. Expecting too much? Jim Yalden expressed the convic- UHF TV - tion that many people have a quite unrealistic impression of overseas UHF TV services. In Britain, for example, the industry tends to regard 30-35km as "deep fringe". At Winchester, he says, about 90km from London, there was no trace of the 1-megawatt London transmitter and no one expected otherwise. Where he was staying, just out of Winchester, a good signal was available from a 500kW transmitter on the Isle of Wight, 25km away. But the house was on the advantaged side of a local hill. Viewers a few hundred metres away on the other side of the hill weren't so fortunate. When visiting a relative in Somerset three years ago, TV reception, according to Jim, was "dreadful" . And there were plenty of other places that were no better; in Wales and parts of Scotland for example. So Britain still faces TV coverage problems, despite something like 70 base transmitters and a host of translators serving the relatively compact country. By contrast, in the NSW 11lawarra area, 30-35km has long been accepted as little more than an average viewing distance for VHF, with the "deep fringe " more like 100km out. That's the sort of expectation that the new UHF service is supposed to live up to, with one base transmitter per channel and a handful of scattered translators. Add to that hassles about the siting of translators and an alleged Questions and Speculation • If UHF coverage, as planned, proves to be inadequate, will the DOTC support the installation of extra translators, as necessary, or will isolated communities be expected to install their own, or rely on transmissions from the satellite? • Some maintain that the mid north coast area will pose even greater problems at UHF than the lllawarra area, by reason of the hilly plateau between the mountains and the sea. Will the DOTC reexamine UHF technical planning for that area, in the light of the emerging situation south of Sydney? • In the ultimate event of a 3-network commercial system covering the whole of Australia, will the participants be obliged to serve isolated communities as well as the larger population centres? • To what extent will viewers Australia-wide, who may be disadvantaged by a changeover from VHF to UHF, be supported by the Government or be obliged to rely on their own resources? DECEMBER1988 45 THEWAYI SEE IT - CTD lack of commitment by the incoming major commercial networks to the fringe areas and the immediate prospect for some remote or isolated pockets of viewers is anything but rosy. Not only may they not receive the incoming networks - if and when they materialise - but they stand to lose one or both of the existing services. Problem areas which have been specifically mentioned range froin deep pockets in the immediate area of the main transmitters, to Kangaroo Valley in the west and to Bateman's Bay in the south. These areas presently get by with a patchwork of VHF signals, direct or via translators. In the face of those and other situations, according to Jim Yalden, there's likely to be "one almighty hell of a scream" on the day they switch off the channel 4 and 5A VHF transmitters - maybe in January or March; who knows? She 'II be right, mate! That's about where we left matters on the morning of September 26, after a couple of phone calls and a round-robin "rag-chew" on the 2-metre amateur band. But on Wednesday the 28th, the MiltonUlladulla Express carried an assurance by the Federal member for Gilmore, John Sharp, to the effect that no viewer in the MiltonUlladulla area would be disadvantaged by the imminent changeover to UHF. It sounded like a political promise of the kind that his constituents most wanted to hear but it was reportedly based on a firm assurance from the Department of Transport and Communications. When asked whether everybody in the south eastern television market would receive improved or at least comparable services next year, their reply was an unqualified "Yes". Said Mr Sharp: "They have assured me that many people will in fact receive improved service and certainly no one will lose what they already have, even if this is only a relatively poor existing signal". While some viewers may have been reassured, I gather that the 11lawarra technical bods reacted otherwise. But unlike the one-time gentry with their snuff boxes, they are passing around pinches of sodium chloride! How could the Department possibly give such an undertaking in view of the limited penetration of UHF signals, the unresolved fading effects, the distances involved and the strictly limited number of translators envisaged? Perhaps even Mr Sharp was reaching for the salt cellar when he added [as quoted): "I will certainly remember this guarantee and it is gratifying the Department has finally been able to provide such an assurance". In the meantime, I did not invent the questions posed in the accompanying panel. I've simply summarised what has been put to me. See what you think. Colourising B& W films From UHF TV I return to the subject of computer-aided colour reprocessing of black and white films mainly intended for presentation on television. Faced recently with the screening of such a film (correction, video tape), TV presenter Bill Collins launched into the usual apologia, acknowledging objections to the process voiced by some film makers and reminding purist viewers that they had the option of turning off the colour and viewing the original monochrome image. How much longer do we have to put up with this tedious preamble at every mention of a computer colourised film? I seriously doubt that many viewers would have followed Bill Collins' suggestion to kill the colour - or that he really expected them to. Because I had other things to do, I didn't watch the feature right through but I did view it for long enough to register whether or not the colour was so patently artificial as to compromise the original image. In fact, from what I saw it was ordinary enough for a non-alerted viewer to accept it as just another colour print. That was certainly the aim back in 1977, when the first-ever computer colourised documentary footage of World War II was intercut with new footage in a mini series on Dwight Eisenhower , featured by the ABC [American Broadcasting Company). Millions of viewers didn't notice the difference between the two, simply assuming - if they thought about it at all that the documentary material had also been shot in colour. For Ralph Weinger and Donald Havens, credited with the early development of the system, it was exactly the reaction they wanted. Despite this, quite a few film makers, actors and purists have condemned the process as akin to sacrilege and sought to raise legal barriers to restrict its use. Sure, serious black and white photography may qualify as an art form, with an arguable right to be respected as such. Some actors may also reasonably object to their person and work being artificially prettied-up and time-shifted out of the era in which they worked. One can't blame the various parties for pursuing whatever rights they may have in the matter - but enough is enough. The fact is that most early films were shot in black and white There's likely to be one almighty hell of a scream on the day they switch off the channel 4 and 5A transmitters maybe in January or Morch; who knows. 46 SILICON CHIP because colour was not a viable option at the time. When they appear on the TV screen today, the lack of colour is a constant reminder of their age - like a travelling subtitle: "This is an old film, to be watched only as a last resort". Many such films may not be suitable for present-day showing, or of sufficient merit to justify expensive reprocessing. But where they are, let's drop the apologetics and enjoy to the best possible advantage the cinematic products of other days. Let's be thankful for modern computer and digital technology which makes it possible to minimise some of the print faults in old "flicks", to reconcile dissimilar frame rates, clean up noisy sound tracks and add credible colour. That way, they might be justifiably rescued from musty vaults or from TV time slots in the wee, small hours. Optical fibre links But enough of television, films and video tape. Here's something for audio types to ponder. That well known hifi buff, Auric Lugg, has discovered that thanks to the near-magic of solid-state integration, opto coupling components for audio systems have become available: small, efficient and (for him) affordable. He looks quizzically at the cable links between the various components of his domestic hifi system. They're good quality cables, every one of them tipped with gold-plated plugs, fitting into gold plated sockets. Inductance, capacitance and resistance are demonstrably much too small to adversely affect the signal. But Auric Lugg's curiosity knows no bounds and he invests in two sets of the new opto couplers, along with two half-metre lengths of suitably terminated optical fibre cable. Following the instructions very carefully and very methodically, he substitutes the new opto coupling devices for the original metallic sockets and cables feeding the main amplifier. This done, he switches on and professes to be absolutely amazed by what he hears. The difference is not of the subtle kind, revealed only by careful A-B testing. It's as if a veil had been lifted from between him and the loudspeakers. The sound, he says, is dramatic, stunning, unbelievably pure! The noise, distortion and unmusical harshness characteristic of wire connections has been totally eliminated by installation of the fibre optic cables, which are claimed to be completely free from such imperfections. I jest? I'm letting my imagination run riot? No! I've simply assembled a word picture from phrases currently being used to promote the provision for optical links . in the latest generation of up-market audio gear. You can swallow it if you like. Me? I'm taking it with a grain of salt. Fibre optics are OK I am not by any means opposed to fibre optics, as such. It stands out as a breakthrough in communications technology. • The National Australia Bank, for example, has installed an optical fibre network in its Melbourne administrative centre to interconnect computer terminals, the communications network and the building control system. • Optical fibre ea ble has been laid around Sydney Airport to link the various radar transmitters with the operations centre. Unlike the coaxial cable which it replaces, it is inert to humidity, corrosion, earth loops, electrical noise and lightning strikes. • Optical fibre cable was chosen in preference to coaxial cable to bring together at the control building the very wideband signals from the 0 six mobile dishes forming the Australia Radio Telescope at Culgoora. • Over the next few years, Australia's internal and external communications will become progressively more dependent on optical fibre cables. • In the October issue, I reasoned that the concept of "fly by wire" should be replaced by "fly by optical fibre" in the quest for greater safety. In short, fibre optic technology offers considerable advantages in terms of economy (especially over long distances), physical durability, exceptionally wide bandwidth, high traffic density and a high degree of immunity from electromagnetic interference, natural or man-made. None of those advantages has any obvious bearing on the transfer of audio signals over the metre-long (or less) paths in a home hifi system. It may be trendy but I fail to see how the substitution of an optical link for a normal, adequate wire link can contribute anything to the subjective quality of the signal. In due course, mass produced optical fibre hardware and connecting cable could conceivably become tidier and easier to handle than shielded copper cable. It may also get designers off the hook by isolating signal paths from considerations to do with equipment earthing (or non-earthing) for safety reasons. In the meantime, optical links may provide a novel sales feature to distinguish the latest models but as an effective way of removing yet another in that seemingly endless sequence of acoustic veils, I'd need to be convinced. ~ ft~ uo/. ,,~ . ~ :..OU rll; uv1 - ~ "CJIIPIIII""~ RCS Radio Pty Ltd is the only company which manufa.ctures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 4-HOUR TURNAROUND SERVICE DECEMBER 1988 47 ONLY 3 WEEKS TO 601 Ho Ho Ho. That's Santa laughing at all the bargains he's picked up at his friendly Dick Smith Electronics store. Santa knows that Dick Smith Electronics has everything for the electronics enthusiast - and much, much more besides! Christmas morning and you forgot the batteries! Wouldn't you be popular? All those wonderful new Wizz-bang goodies and not a battery to make them Wizz and bang! Plan ahead - if you get batteries early, you won't forget. And if you get Nicads, they can be all charged up and ready to fire . ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• USE NICADS: THEY'RE CHEAl'ER! Sure they cost more than ordinary batteries. But you can charge Nicads hundreds of times so compare the price of hundreds of ordinary batteries! You'll save ................................................................ Standard Nicads TOOLS ARE ALWAYS TREASURED! 180mAh ..AAA" Size Cat S-3305 ..AA" Size 500mAh Cat S-3300 'C" Size "D" Size 1.2Ah Cat S-3301 "9V" Size 110mAh Cat S-3309 1.2Ah Cal S-3303 s495 s475 $1195 $1195 S1695 High Capacity Nicads 600mAh S!j95 "AA" Size Cat S-3312 2.0Ah ..C" Size Cat S-3311 s1495 4.0Ah "D" Size Cat S-3310 s1595 "SubC" Size GELL CELLS Ideal for alarms & general purpose usage. 12V 12V 1.2Ah 1.9Ah 35 37 95 Cat S-3315 1 95 CatS.J3t61 12V 12V 2.6Ah 6.5Ah 3895 Cat S-3320 1 CatS-3322 '5595 CHARGERS TO SUIT: ln-situ or loose • these chargers will see your NiCad batteries right! Plug-Pack: Standard: Super: Suitable for most general purpose in-situ (ie batteries stay inside device) charging. Handles 6 to 10 standard or high capacity "AA" cells. Cat M-9517 Handles all types and sizes of Nicads from AA through to 9V; charge up to 8 cells at once. Automatically senses size. includes charge test meter Cat M-9505 Specifically for high capacity N1cads; also sences size and adjusts charge automatically. (Do not use for standard Nicads except AA Size). Cat M-9506 -1~ s3995 FUNWAY: THE BOOKS $495 Fun Way Into Eleclronlcs Vol 1. 20 exciting projects to build• no soldering. Cat B-2600 Fun Way Into Electronics, Val 2. 20 more fascinating proiects • and we teach you to solder. Cat B-2605 The Ultimate Hi-Tech Present A Computer! But not just any computer• a superb ACER 500+ from Dick Smith Electronics. Australia's best value in an IBM compatible - and our low prices INCLUDE a beautiful soft-white monitor. Three models to choose from. you choose the configuration you want to suit your needs. And don't forget, you can always upgrade your ACER later! Acer 500+ Complete from only s995 Fun Way Into Elllctronics, Val 3. 5695 $695 10 "high tech" projects using integrated circuits. Cat B-2610 INTO RADIO? TRY A SCANNER The Ultimate: FRG9600 __. · What a scanner! It Hand-Held Action: Bearcat 100XL covers all UHF from 300 to 950MHz - so it ~t includes virtually evervthing you want to NORMALLY $1199 hear! Programmable, UNTIL XMAS JUST memories, even controllable! The go-anywhere scanner that means you can actually go to the action while you 're listening! 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HOW ABOUT ACRO? ea Cat W-2060 Merry Christmas and a bright and prosperous New Year ... from all at Dick Smith Electronics. ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ DIESEL SOUND GENERATOR FOR MODEL RAILROADS This Diesel Sound Generator produces the deep throbbing sound of today's modern diesel electric locos, complete with turbo boost and alternator whine. By GREG SWAIN & JOHN CLARKE While today's model railroads can look startlingly realistic, the illusion is not helped when those locos start to move off with a heavy train behind. Instead of the penetrating sound of turbo-charged diesels with wide-open throttles, all you hear is the tinny sound of miniature motors and gear mech- anisms - nothing like the real thing. If you're modelling in O scale (43:1) or HO (87:1) it is possible to build sound generator circuits into the loco or a following wagon but they always have a problem. Because they can only use the smallest of speakers, they just don't have enough grunt. They're not loud enough and their bass output is non-existent. · And if you model in the increasingly popular N-gauge (160:1), an on-board sound system is completely out of the question - the rolling stock is just too tiny. So we've had a look at the problem of sound for model railroads. Our new Diesel Sound Generator is the answer. It can be used with any scale loco and does not rely on teensy speakers built into the loco. It uses one or more speakers, as large as you like, dotted around your layout. And it incorporates circuitry to monitor where your loco is so the sound can follow it around the layout. We built the diesel sound generator into a plastic instrument case but you can dispense with the case and simply mount the PCB under your layout. The amplifier PCB is housed in the small plastic case at right. 50 SILICON CHIP The Diesel Sound Generator is designed to mate with the Railpower train controller described in April 1988 but can be used with any train controller that varies the track voltage (that leaves out Command Control systems). It requires little wiring to add it to your layout and you can build it in a simple or more complex form to suit your needs. So what sort of sound do we get from a real life diesel locomotive? The sound is really quite complex but consists mainly of lowfrequency exhaust beats and turbocharger whine, coupled with a small amount of high-frequency alternator hum. Our circuit simulates all these effects to produce a very realistic diesel loco sound indeed. But we haven't just settled for a circuit that makes realistic diesel loco sounds. That wouldn't be good enough. For starters, this new design automatically adjusts the pitch of the diesel exhaust according to the throttle setting. It does this by constantly monitoring the track voltage. The circuit also automatically adjusts the volume according to the location of the loco and can even vary the location of the sound source. It does this by using trackside sensors to monitor the location of the train on the layout. This information is then fed into the circuit to produce the appropriate response. 12VAC TRACK SOUND GENERATOR 4 DC 3 CONTROL 2 +12V GND SIGNAL SINGLE AMPLIFIER TRAIN POSITION SENSORS 1 2 4 □ osE~SOR Fig.1: this is the layout to go for if you intend using a single amplifier and loudspeaker. The sensors monitor the location of the loco on the track. This information is then used to derive a DC control voltage which sets the amplifier volume. Alternative layouts Figs.1 & 2 show the two basic layouts you can use for the Diesel Sound Simulator. In Fig.1, four trackside sensors monitor the location of the loco and this information is fed to the sound generator board to produce a DC control voltage. This voltage is then used to control the volume of a single audio amplifier. By using this simple arrangement the volume from the amplifier stage fades (up or down) to one of four different levels as the loco passes each pair of_ trackside sensors. In a practical layout, you would arrange for the sound level to increase as the loco moves towards you and then decrease as it moves away. The two halves of the photo-interruptor are mounted on opposite sides of the track. When the loco passes between them, it breaks the infrared light beam. This causes the amplifier volume to increase for that sector. But although this can produce quite realistic effects, it cannot change the apparent location of the sound source, as the loco moves around the layout. To simulate a moving sound source, you need to use the arrangement shown in Fig.2. Once again, four trackside sensors are used but each of these now controls a separate audio amplifier with its own loudspeaker. In practice, it's simply a matter of positioning the four loudspeakers driven by the amplifiers to produce DECEMBER1988 51 ~ ::c: ..... z n 0 t==: ..... 0 CJ':) ""NI 12VAC .033 TRACK VOLTAGE .,. IN 14 .,. 16 17 • ,.W- 100 .J,,t • 10 16VW+ 16VW+ 1our • ~,t K LED A +12v 5.6k 0.27! 4.7k .,. +12v f .,. 1° l:w:I lli] LOW FREQUENCY REPETITION 1 I INPUT PARALLEUiJ! SERIAL l16 DIESEL SOUND GENERATOR .,. OUTrr--,, IC2 4021 1.L..11LJTh 11 SERIAL 3 08 IN 3 COMP I 10 CK 12 7 _III_H 470k r------~~-...-.,_......,______ 10 .WVR2 16VW"'I"!20k THRESHOLD '14 IC1 SIG !Nit'---- 4046 vco 4.7k +12V GNU ~~ VIEWED FROM BELOW eQc 8 10kl 680k 8200 NOISE SOURCE +12Y 0.1T • .039t ALTERNATOR SOURCE 470k TRAIN POSITION SENSORS +12V .,. o.1I .,. +12V .,, .,. 10~ l13 4 AMPLFIER --0 AMPLIAER 3 .,. +12V .,, 02 03 AMPLIAER 3 04 AMPLIFIER 1.5k ,10 15 02 .,. .,. 74C14,40106 :g IC6 40175 IC4c/s\ ? 112 03 -: .,. IC411J"s t 113 04 0.1.;: CLRl 1 680k +12V 8!l SPEAKER .,. t6,,V~~ 220 AMPLIAER 4 -:- t t. 't ~ AMPLIAER 2 2.2 .J: 16VWJ rJ: 16VWJ 220 12VAC TRACK l l SOUND GENERATOR +12V GND SIGNAL AMPLIFIER 1 TRAIN POSmON SENSORS AMPLIFIER 2 AMPLIFIER 3 AMPLIFIER 4 1 2 3 4 +12V +12V TD LOUDSPEAKER TD LOUDSPEAKER TD LOUDSPEAKER 2 3 4 □ ed around the loop, from pin 11 through to pins 3 and 12, and via the XOR gate (pins 14, 3 & 2 of ICl) back to pin 11. Thus, IC2 and the XOR gate in ICl generate a pseudo random pulse train and the speed at which this is generated is controlled by the VCO. This gives a realistic "hunting" quality to the diesel sound. The output from the noise generator is taken from the Q8 output of IC2 and applied to a low pass filter consisting of a 4. 7k0 resistor and 0.27µF capacitor. From there, the signal is fed to the pin 5 input of buffer amplifier IC3d. White noise source SENSOR 4 SPE:KER[J1 □ Fig.2: this alternative track layout uses four separate audio amplifiers and four loudspeakers. The loudspeakers are mounted at appropriate locations around the track to simulate a moving sound source. the best effect as the loco moves around the track. The volume from each amplifier can be adjusted by changing a single resistor value. How it works Most of the circuitry is contained in eight low-cost ICs. Fig.3 shows the details. ICl and IC2 form a pseudorandom noise generator and together provide the low frequency exhaust beats so characteristic of a diesel locomotive. ICl is a 4046 phase locked loop (PLL) and contains a voltage controlled oscillator (VCO) and an exclusive-OR (XOR) gate which is normally used as a phase comparator. In our circuit though, ICl is not used as a phaselocked loop. We are only using the VCO and the XOR gate. VRl, the 470k0 resistor and the .033µF capacitor set the overall fre◄ Fig.3 (left): three separate noise sources are used to simulate the diesel sound. ICl & IC2 provide the low frequency exhaust beats, IC3 provides the high frequency exhaust noise, and IC3a & IC3b provide the alternator whine. quency range of the VCO, while its actual frequency is set by the DC control voltage applied to pin 9. This control voltage is derived from the track voltage via a bridge rectifier (D5-D8) and a voltage divider consisting of two 4. 7k0 resistors. In this manner, the speed of the VCO is controlled by the throttle setting on the train controller. The higher the setting, the higher the frequency of the VCO. When the throttle is closed, the control voltage on pin 9 is at a minimum and the VCO runs at its minimum value of around 300Hz, thus setting the engine idle speed. The VCO output appears at pin 4 of ICl and clocks IC2 which is a 4021 shift register. When the circuit is first switched on, pin 9 of IC2 is momentarily pulled high via a 0.lµF capacitor. This loads an 8-bit number into the shift register (as determined by the wired connections to pins 1, 4, 5, 6, 7, 13, 14 & 15). Pseudo random pulses The VCO signal is fed to pin 10 of IC2 and thereby controls the speed at which the 8-bit pattern is shuffl- OK, so we have our low frequency exhaust beats. We now have to simulate the high frequency exhaust noise and this task is performed by transistor Ql and op amp IC3c. Ql is connected as a reverse biased diode (ie, the base-emitter junction is reverse biased) which makes it into a good "white noise" source. The resulting noise produced by Ql 's controlled avalanche breakdown is AC-coupled via a .047 µF capacitor to pin 10 of IC3c which is a non-inverting amplifier with a gain of 69. A voltage divider consisting of two lM0 resistors sets the bias at pin 10 of IC3c to half supply. The amplified output of IC3c appears at pin 8. From there, it is fed via a l0k0 resistor to pin 5 of IC3d where it is mixed with the low frequency exhaust beats. Alternator whine Unlike the previous two noise generator circuits, the alternator whine only comes into play when the track voltage reaches a predetermined level. This provides more realistic simulation, since alternator whine only becomes apparent after a diesel loco gets up speed. IC3a and IC3b provide simulation of the alternator whine. IC3a functions as an amplifier and controls Schmitt trigger oscillator IC3b via diode D9. Let's take a closer look at how the circuit works. Diodes D5-D8 provide full-wave DECEMBER 1988 53 t-1- 12VAC tTRACKt ® HH ,rh~~~® c~r-c l ~ ... ;~ 8 ®~®C¥;]' 1000uF FL 12 + v~O~R2 GNO_l...." SIGNAL- I _ ~ e ~ --mE}-l [ ~470 L~t2; ] i .l!; :g ~ ~ 09~ ~ ;! i;j liJ ~ ffi ~~ 1 -!llliJ- 10k --rrz:o..---cm::J- .i: 8 I] - --ruo,. ~ ~~ I ~ <at>) .,:e !.1:; .. ®~ /'.!'\6 ~ .l!; ~ ~~ ~ e - l3 CONTROL I TD AMPLIFIER 1 - - - - TO AMPLIFIER 4 ..mo,. A oc VOLUME 1 - T D AMPLIAER 3 I -TOAMPLIFIER2 ~ 1 K• E• K• E• K• E• K• Ee ~ ~ A• C• A• C• A• C• A• Ce OP1 __ OP2_ OP3_ OP4_ _ _ _ _ _ _ _ _ _ _ __. Fig.4: here's how to mount the parts on the sound generator PCB. Make sure that all parts are installed the right way around and use PC stakes to terminate the external wiring connections. The 12VAC supply can be derived from the train controller. rectification of the track voltage as previously described. The output of this bridge rectifier is then fed to a voltage divider, filtered by a lOµF capacitor and applied to pin 3 of IC3a. Trimpot VR2 sets the threshold at which the circuit begins to operate by applying a preset voltage to pin 2. So what does this all mean'? It means that, at low throttle settings, the voltage on pin 3 of IC3a will be less than that on pin 2. Thus, the output (pin 1] will be low and diode D9 will be forward biased. As the throttle is progressively opened, the voltage on pin 3 rises above the pin 2 threshold and IC3a functions as an amplifier with a gain of 2. When its output reaches about 0.66 of the supply rail, D9 will be reverse biased. D9 determines whether Schmitt trigger oscillator IC3b functions or not. The 470k0 feedback resistor between pins 14 and 12 sets the level of hysteresis, whilst a voltage divider consisting of two more 470k0 resistors sets the midpoint voltage on pin 12 to half supply (ie, to + 6V). 54 SILICON CHIP When D9 is reverse biased, IC3b oscillates at about 2.4kHz, with the .039µF capacitor alternately charging and discharging between 0.33Vcc and 0.66Vcc (ie, between 4V and BV). This signal simulates the alternator whine and is fed to pin 5 of IC3d via a 150k0 resistor where it is mixed with the noise signals from IC2 and IC3. However, when D9 is forward biased (ie, when the track voltage is below the threshold level], the voltage across the .039µF capacitor is clamped to 0.5Vcc. As a result, IC3b stops oscillating and the alternator whine ceases. DC volume control IC3d functions as a non-inverting buffer amplifier and is used to drive the following audio amplifier stages. For the sake of clarity, our circuit shows only one audio amplifier. It consists of DC volume control IC7, 741 op amp stage ICB, and transistors Q6 and Q7. If you want to add additional amplifiers, all you have to do is duplicate the circuit based on these components. IC7 is an MC3340P "electronic attenuator" chip from Motorola. It functions as a DC volume control. As the voltage at pin 2 is increased from 3V, the gain is reduced from + 13dB to below - 70dB at around +5V. In this circuit, a 470k0 resistor at pin 2 sets the maximum attenuation (ie, it sets the minimum volume from the loudspeaker]. To increase the volume when the train passes a set of trackside sensors, all we have to do is to switch another resistor in parallel with the 470k0 resistor on pin 2. This job is performed by transistors Q2-Q5 but more about that later. The output from the attenuator is coupled directly to pin 3 of ICB, which is a 741 op amp. This in turn drives a push-pull transistor output stage consisting of Q6 and Q7. From there, the signal is AC-coupled via a 220µF capacitor to an BO loudspeaker. Negative feedback for the amplifier is via the 1.5k0 resistor connected between the commoned emitters of Q6 and Q7 and pin 2 of ICB. Together with the associated lkO resistor, this sets the overall gain of the amplifier to 2.5. The associated 2.2µF capacitor rolls off the amplifier low frequency response below 70Hz. Trackside sensors Four photo-interrupters, OP10P4, are used as trackside sensors to detect the position of the loco. These photo-interrupters consist of an infrared LED and an NPN Darlington phototransistor. Normally used as position sensors in printers for computers, they are cut in half and the halves are located on opposite sides of the track (see Figs.1 & 2). The infrared interrupter LEDs are supplied with current via a 4700 resistor from the 12V supply. The Darlington transistors have their collectors connected to the + 12V supply and their emitters connected to OV via 1 BOkO resistors. When under full illumination from the LED, the phototransistor conducts and its emitter is pulled high. When the light is interrupted the voltage at the emitter drops to OV. The four phototransistor outputs This view shows how we mounted the sound generator PCB inside a standard plastic instrument case. Most readers will probably prefer to mount the board out of sight, underneath the layout. The external wiring can be run using rainbow cable. are monitored by Schmitt triggers IC4a to IC4d. The outputs of the Schmitt triggers connect to the data inputs of IC6, a 40175 quad D-type flipflop, and to the inputs of quad input NOR gate IC5, a 4002. Data storage IC6 is the key component in determining which amplifier's gain is increased. For the system to work properly, the amplifier associated with a particular sector of the railroad layout must increase its gain when the train enters that sector. At the same time, the amplifier associated with the previous sector where the loco was present must fade down. In addition, the circuit must be able to cope with any change in direction that the loco might make, To simplify external connections, we terminated all the wires from the generator board on two multi-way insulated terminal blocks. These are recommended even if you don't use the plastic case. DECEMBER1988 55 DC VOLUME CONTROL GNO sa SIGNAL +12V SPEAKER Fig.5: parts layout for the DCcontrolled audio amplifier. The + 12V supply is derived from the sound generator PCB. Depending on your requirements, you can build up to four of these audio amplifiers to go with the sound generator PCB. We mounted the amplifier in a small plastic case but it could also be mounted in the same case as the sound generator board or mounted under the layout. For best sound output, the loudspeaker(s) used should have good bass frequency response. If the high frequency response is excessive, you can chop it back by reducing the 680kn feedback resistor between pins 8 & 9 of IC3. as it enters, leaves and re-enters any of the four sectors. Whenever the loco passes between one of the trackside sensors, the output of the associated Schmitt trigger (in IC4) goes high. Normally, unless the train stops light transmission across one of the four interrupters, all four Schmitt triggers will be low and the output of the quad input NOR gate IC5 will be high. When one of the Schmitt trigger 56 SILICON CHIP outputs does go high the output of IC5 will go low. This low signal is delayed by the 15k0 resistor and 0.1µ,F capacitor and then passed to the input of Schmitt trigger IC4e. The output of IC4e then goes high and clocks the four D-type flipflops. Let's say that the output of IC4b has gone high. When IC4e goes high, this high signal will be "latched" at the Q2 output of IC6, pin 7. This will turn on transistor Q3 which will then pull down its callee- tor resistor. This increases the gain of amplifier 2. If the loco then moves to interrupter OP3, IC4c's output will go high, and IC6 will "latch" the high signal through to pin 10. This will turn on Q4 which will increase the gain of amplifier 3. In the meantime, Q3 will have turned off and the gain of amplifier 2 will have been reduced. The "CLR" (clear) input at pin 1 makes sure that IC6 is properly set to zero from the start. At switch-on the 0.1µ,F capacitor has the effect of pulling pin 1 low which sets the Q outputs (pins 2, 7, 10 and 15) low. The 680k0 resistor then charges the 0.1µ,F capacitor to +12V so that pin 1 is high and IC6 can work normally. This means that until a loco passes a photo interruptor, all amplifiers will be at minimum volume. To control the gain of IC7 (or the MC3340 associated with each separate audio output stage), transistors Q2 to Q5 switch in a resistor to ground. The 4.7k0 resistor at the collector of Q2 sets the volume at maximum, while the 15k0 resistor at Q3 sets the volume at a minimum. The 220µ,F capacitor on pin 2 of IC7 ensures that the gain changes are not too abrupt. If you want even slower fading up and down of gain, increase this capacitor further. Power supply Power for the circuit will normally be supplied from the low voltage transformer which feeds the train controller. Normally, this transformer will deliver between 12 and 20V AC. This is fed to the bridge rectifier consisting of diodes Dl to D4. The bridge feeds a 1000µF filter capacitor and 7812 3-terminal regulator to provide + 12V. A l0µF capacitor at the output of the 7812 regulator ensures its stability. Another 100µF capacitor across the supply but remote from the regulator provides further decoupling of the supply for the ICs. Construction The Diesel Sound Generator and the amplifier are made up on separate printed circuit boards. These measure 117 x 130mm (code SC09-1-0988-2) for the diesel generator and 60 x 47mm (code SC09-l-0988-1) for the amplifier board. For a minimum set-up you will need one generator board and one amplifier board. For the most complex set-up you will need one generator board and four amplifier boards, together with associated loudspeakers. Most readers will probably prefer to mount the printed boards beneath their track layout. However, both boards will fit inside standard plastic cases, as shown in the photos. The sound generator board fits into an instrument case measuring 200 x 158 x 68mm (Altronics Cat. H-0480) while the amplifier fits in a zippy case measuring 83 x 54 x 28mm (Altronics Cat. H-0101). Assembly of the two PCBs is quite straightforward just follow Figs.4 & 5. Take care to correctly connect the polarised components such as the diodes, ICs, transistors, the 3-terminal regulator, and the electrolytic capacitors. Testing To simplify the connection of wiring, we terminated all the wires from the generator board on two multi-way insulated terminal strips. For the initial test, do not connect the DC volume control line(s) from the generator board to the amplifier. Instead, connect a 4. 7k0 PARTS LIST Diesel Sound PCB 1 PCB, code SC09-1-0988-2, 117 x 130mm 1 plastic instrument case, 205 x 158 x 68mm (optional) 1 1 6-way insulated terminal block 1 12-way insulated terminal block Semiconductors 1 40175, 7 4C175 quad D flipflop 1 40106, 7 4C14 hex Schmitt trigger 1 4046 phase lock loop 1 4021 8-stage static shift register 1 4002 dual 4-input NOR gate 1 LM324 quad op amp 1 1 N914, 1 N4148 signal diode 4 1 N4002 1 A diodes 1 7 81 2 3-terminal regulator 4 BC337 NPN transistors 1 BC548 NPN transistor 4 STIN3101 or equivalent photo-coupled interrupters Capacitors 1 1 000µF 25VW PC electrolytic 1 1 00µF 16VW PC electrolytic 2 1 0µF 16VW PC electrolytic 1 0.27 µF metallised polyester 4 0 . 1µF metallised polyester 1 .04 7 µF metallised polyester 1 .039µF metallised polyester 1 .033µF metallised polyester Resistors (0 .25W, 5%) 2 x 1 MO, 3 x 680k0, 6 x 470k0, 1 X 330k0, 4 X 180k0, 1 x 150k0, 2 x 15k0, 9 x 1 OkO, 1 x 6.8k0, 1 X 5.6k0, 4 X 4. 7k0, 1 X 8200, 4 X 4700, 1 X 200k0 miniature vertical trimpot, 1. x 20k0 miniature vertical trimpot Audio Amplifier 1 plastic zippy box, 83 x 54 x 28mm 1 PCB, code SC09-1 -0988-1 , . 60 x 47mm Semiconductors 1 MC3340P DC attenuator 1 741 op amp 1 BC337 NPN transistor 1 BC327 PNP transistor Capacitors 3 220µF 16VW PC electrolytic 1 2.2µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 1 680pF ceramic Resistors (0 .25W, 5%) 1 x 470k0, 1 x 1.5k0, 1 x 1 k0 Miscellaneous Loudspeakers, hookup wire, tinned copper wire, solder etc. The LED section of the photointerruptor has a small diode symbol moulded into the plastic housing. The photo-interruptor must be cut in half and the two halves mounted on opposite .sides of the track. resistor between the DC volume control input to the amplifier board and the 0V line. With all connections made, switch on the power and check that the 7812 regulator has + 12V at its output. If all is operating correctly, the diesel sound should be emanating from the loudspeaker. The pitch of the diesel sound should increase as the train controller's output is increased. You can set the maximum pitch, to coincide with the maximum throttle setting, using VR1. When setting VRl remember that DECEMBER 1988 57 I ~ -~ ~, I 0 . SC09-1-0988-2 L '7°1 l. '7'7 58 SILICON CHIP L.= Fig.7: actual size artwork for the amplifier PCB. The actual volume level is dependent upon the resistor connected to the DC volume control input. A 4. 7k0 resistor gives maximum volume while a value of 15k0 gives the minimum volume. The values shown were used in our circuit but can be altered to suit a different track layout. Options Fig.6: here is an actual size artwork for the sound generator PCB. Ready etched boards are available from the usual sources (see hack page). the large diesels in locomotives usually run at no more than about 1100 RPM when at full power. So don't make it sound like a racing car at flat-chat. Adjust VR2 so that the hum cuts in soon after the diesel sound passes idle speed and as the loco begins to move. The remainder of the circuit can now be tested by connecting up the optical sensors and DC volume control lines to the amplifier(s). The track sensor is made by cutting a STIN-3101 photo-interrupter in half. We obtained our sensor from Geoff Wood Electronics but equivalents are readily available elswhere. Alternatively, if you wish, you can use a separate infrared LED (LD271, CQY89A) and infrared photodiode (BPW50, BP104R) or NPN phototransistor (TIL81). The advantage of the interrupters is that they are easy to ...~. mount and conceal as trackside structures. Cut the interrupter in half between the light emitting diode and the phototransistor. Use a finebladed hacksaw for this purpose and file the cut edges to provide a smooth finish. The resulting separate devices are mounted directly opposite each other on each side of the railway line. They must be mounted on the same plane and should be square on to ensure maximum sensitivity. Once the sensors are located and wired to the PCB, the circuitry is ready to be tested. When power is first applied, the diesel sound should be muted. For each interruption of a sensor, the volume should adjust to another volume. When used with separate amplifiers, a different amplifier should operate for each sensor and with a different volume. Besides the two optional set-ups we have shown in Figs.1 and 2, a number of other variations can be added. For best sound output, the loudspeaker should have a good bass frequency response. If you are using properly baffled speakers you can obtain even better bass response by modifying the amplifier board. As it stands, the amplifier circuit cuts off at about 120Hz. To lower this to below 40Hz, increase the 220µF output coupling capcitor to 470µF, the 2.2µF feedback capacitor to lOµF and the lµF input capacitor to 2.2µF. Note that this is only worth doing if your speaker(s) have useable bass response to 40Hz. It is not necessary to use speakers with good high frequency response. If you do so, you will probably find that the high frequency noise output from the circuit is too obtrusive. You can chop it back by reducing the 680k0 resistor between pins 8 and 9 of IC3c. To make a noticeable reduction, try a value of 100k0. ~ Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. '------------ Charger for 12V gel batteries Standard 12V chargers intended for car batteries should not be used for charging 12V gel cells. They charge at too high a rate and they do not cease charging when the recommended maximum battery voltage is reached. The circuit presented here limits the charging current to 600 milliamps and cuts the current to a low value when the battery reaches full charge. Power for the circuit comes from a 2155 1A 15V transformer which feeds four diodes in a bridge rectifier and a lOOOµF filter capacitor. This produces a filtered but unregulated supply of about 21 to 23 volts DC, depending on the transformer. This unregulated supply is then fed to an LM317 adjustable 3-terminal regulator which functions to limit both the maximum output voltage and the maximum output current. Normally, when a battery is on charge, the circuit will be acting as a current source. Then, as the battery reaches full charge, it A-/ 240VAC T N 12V : 1000 25VW E • + ..L. B ELJc VIEWED FROM BELOW OUT Fig.1: when the voltage across the Hl resistor exceeds 0.6V, Qt turns on and reduces the voltage across the 1.2k!l resistor and 2000 trimpot. This, in turn, reduces the voltage from the LM317. will change over to maintain a constant voltage. The circuit works as follows: when the battery has reached full charge, Ql and its associated base and emitter resistors can be considered to be short-circuited. The output voltage is therefore determined by the 1200, 1.2k0 and 2000 trimpot connected to the output of the LM317. The 2000 trimpot is there to set the output voltage to exactly 14.2 volts. When the battery is on charge, Constant current nicad charger Some of the cheap commercial nicad chargers are little more than a rectified AC power supply with a series limiting resistor to restri~t the current supplied to the charging cells. While these circuits do function as a charger they do not provide an accurate constant current to the cells, especially if the number of cells can be varied. Consequently, it can be difficult to accurately time the charging to ensure that the cells are not over or under charged. 2155=----, 5V the output current from the regulator develops a voltage across the rn resistor. If this voltage exceeds 0.6V, transistor Ql turns on reduces the voltage across the 1.2k0 resistor and 2000 trimpot and so reduces the voltage from the regulator circuit as a whole. In practice, the circuit settles at a current of about 0.6A until the battery is almost charged. As the battery voltage reaches 14.2 volts, the current through it drops to a negligible value. - 01 1N4002 50mA 12V PLUG-PACK 1 .,.. Both cases can lead to a shorter nicad cell life. The circuit shown here is designed to charge up to 6 AA 500mAh nicad cells in series using a precise constant current source. The accuracy of the charging current allows discharged cells to be completely charged in 15 hours. .. ~ + + T + 10 25VW+ NiCad CELLS I ...L.. OUT An adjustable 3-terminal regulator (LM317) is the basis of the circuit. Preceding the LM317 is a diode and 470µF 25VW filter capacitor. These components enable the circuit to be fed with a DC or AC plugpack. If using a DC plugpack it can be rated up to 18V while AC continued on page 67 DECEMBER 1988 59 COMPLETE RANGE MOTHERBOARDS M B1600 M B2B6 120K M B2B6 16 1M MB2B61 6L1M M B28620 1M M B386202 ~l 10MHz XT M /Boa rd,OK RAM Baby 286 M /Board, 12M Hz/0 K Baby 286 M IBoard, 16M Hz/ 1M Baby 286 M /Board, 16MHz/ 1m Baby 286 M /Board, 20MHz/l M Baby 386 M /Board,2 0MHz/2M IC256K 12 IC256K 15 1(2 8710 IC2876 IC2878 IC64K12 IC64K15 IC8087 ICV20 ICV30 256 K RAM Chip - 120nS 256K RAM Chip - 150nS PC Universal Card EPROM Programmer Card Perfect for prototypi ng, with massive 4000 hole w orking area . • Suits PC and AT systems • Bui lt-in data bus, address bus 1/0 line buffers • Universal address decode chi p • D-25 connector $125 249 .00 64 5.00 1645 .00 1495 .00 1895.00 4 500 .00 CHIPS 80287. 10MHz Co-processor 8 0 287, 6MHz Co- processor 8 0 287, 8 MHz Co-processor 64K RAM Chip - 120nS 64K RAM Chip - 150nS 8087 -2. 8M Hz Co-Processor NEC V20 Chip NEC V30 Chip - 10MHz 23 00 19 .90 549 .00 3 15.00 450.00 9 .00 7 50 275.00 29 .00 49 .00 DISK DRIVES DD 1037A D01053 DD1157C DD31 46 H D05 126 DD5146 H DDMCASE $1,'141 0 SWCCSD SW PAINT SWSLl SWSL2 SWSL3 SWWM Disk Drive.NEC 720K,3.5in Disk Drive, NE C 360K Disk Drive, NE C 1 2MB Hard DD, NE C 40MB, 35mS Ha rd Disk Drive, NEC 20MB Hard Disk Drive, NEC 4 0MB S.25 in case - 3.Sin drive 23 5 00 225 .00 245 00 855 .00 495 .00 895 .00 25 .00 SOFTWARE MS DOS V3 .2 - (NEC) CCS Designer CCS Pa1n tshow CCS Symbol Li bra ry No 1 CCS Symbol Library No 2 CCS Symbol l ibra ry No 3 Wordmag1c, Wordprocessmg 80.00 179 .00 55 .00 79 00 79 00 79 00 139.00 This superb EPROM burner comes wit h a high quality ZIF socket and cabling Facilities include the ability to read, write, copy, compare and erase the contents of EPROMs. Compatible EPROMS include: 2716, 2732, 2764, 27128, 27256, 27512, 2804, 2816, 2864, 58064. 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Introductory price is on ly C • All products carry a 14 day money back guarantee ■ All products carry a fu ll 3 months warranty ■ All cards come with full documentation ■ Ring for quantity discounts and tax free prices. ■ Freight $7.50 forfirst item, then $2 .50 for each extra item. Dealer Enquiries Welcome The customer has no idea I often wonder whether the customer ever has the slightest inkling of what a serviceman goes through in tracking down some of Murphy's most vicious creations. But even as I ponder, I know the answer: the customer's thinking is light years away, across a chasm that can never be bridged. And what brought on that little burst of philosophy? Answer - one of the most frustrating and least satisfying exercises I have experienced for a long time. It included just about every negative aspect one could imagine. Quite apart from the technical problems, there were difficult customer relations. These involved, among other things, a reluctance to reveal the set's previous history and a threat to bring consumer affairs into the situation. And I need hardly add that the whole exercise was a complete dead loss financially. The job started out routinely enough; a phone call from a new customer enquiring as to whether I could service her TV set. When I said I would be happy to do so, she said it was a Sanyo colour set which had stopped dead in the middle of a program. Since there didn't seem to be much point in probing deeper right then, I simply suggested she bring the set in to the shop. When she turned up a couple of days later the set turned out to be a Sanyo model CPT 6603, which first appeared about eight years ago. A quick check confirmed that it was quite dead. I made some attempt to delve into the set's history but the customer seemed strangely ignorant in this regard. But I also sensed that she didn't like being questioned. When I opened the set the first thing I found was a blown mains fuse, a 2A slow-blow type. Based on experience, I mentally nominated three possibilities: a faulty degauss thermistor, a faulty horizontal output transistor, or a faulty switching transistor in the power supply. Of these, the last named was the most common. The power supply board mounts vertically on the left hand side of the chassis (from the back) supported by a metal frame. Releasing a screw on the main chassis frees the frame and allows it to be swung to one side. The power supply board can then be freed from the frame, giving access to the copper side. The switching transistor, Q361 (2SC1046L), is mounted on this board on a fairly substantial aluminium heatsink, about 50mm square. This, in turn, is mounted clear of the board by small spacers but is still close enough to allow the base and emitter pins of the transistor to pass through the board to the copper tracks. Knife & blow lamp ~t1<~ ,... .:SU,- 1: AL.~ SE.NSEO SHE. DION~ L-lKE. ge.1N6 qUE~TID~Et>... 62 SILICON CHIP It was as I swung the board clear that I received my first surprise; something which, with hindsight, should have warned me that trouble lay ahead. One glance told me that someone had been there before me. And unless I was very much mistaken, he had been wearing a striped apron and had attacked the board with a butcher's knife and blow lamp. Well, you know what I mean. It was a mess. Excessive soldering heat had destroyed the original cop- . ~Well, to cut it short, it was the same situation as before; a blown fuse, a shot switching transistor, and a couple of faulty diodes. But why? I would have liked to have blamed coincidence but deep down I knew this was clutching at straws. There just had to be a more fundamental reason. I went through the motions of replacing all the components and soon had the set running again. But there was no way that I could return it with the threat of another failure hanging over it. At the very least I owed the customer an explanation for whatever time it was going to take to find the real fault. So I rang the number and this time found myself talking to the lady's husband. And, after giving him a brief resume of the situation, I found him to .be as outgoing as his wife was taciturn. I learned that the set had already failed in a similar fashion on three occasions, and had been repaired by another serviceman, whom he named. Well, that explained a lot of things. I knew the serviceman he mentioned and realised that I erence is the 2S0380 which has the should have recognised his hanhighest ratings of the lot. diwork. He is reasonably clued up I took the precaution of making technically but is sadly lacking the the first test at a reduced voltage skills necessary to handle today's via the Variac, increasing the components. But it explained more that that. voltage gradually in case there was anything else amiss. But everything The fault was obviously a "stinker" went smoothly and I soon had the that had already defied three efset running at normal voltage. forts by the other serviceman until, I ran it for several hours that apparently, the customer became day, spent some time the next day fed up with the situation and sought cleaning up the butchery as best I out someone else - Yours Truly. could, then ran it for a couple more None of this did anything to cheer hours. Then I rang the customer meup. (I learned later of a further comand told her it was ready. She called in later, paid the bill - it was plication. The husband and the seraround $70 - and collected the set. viceman were golfing buddies. One can imagine the conflict that situaAnd that was another one down. tion created in the husband's mind. It's not that simple And what of the domestic situation? Oh yeah! I wouldn't be writing While I sensed a lack of agreement, this had it been that simple. A cou- I couldn't decide whether he was a ple of weeks passed and then the henpecked husband or she a roosterpecked wife). lady was on the phone with the complaint that the set had failed But right then I had to content again and, according to her, it was myself with pointing out, as the same fault as before. I was well diplomatically as possible, that he aware of the significance of that might have saved a lot of time and remark but I wasn't going to argue trouble - and money - if I had at that stage. I simply invited her to known the set's history in the first bring the set in again. place. And I added that it might _ _._, per tracks to the transistor pins and these had been replaced with short lengths of heavy scrap wire, clumsily soldered into place. And I could see that several other components had been removed for testing or replacement. There was no damage here but one could see where he'd been. I made a mental note to clean things up later. I didn't want anyone seeing that mess after I hq.d handled the set. But first I had to fix the fault. It took only a moment to confirm that I had picked it in one; Q361 was a dead short between collector, base and emitter. This type of failure is not unknown in this model and I had seen it often enough before to know that any one of three diodes D362, D363 and D364 - could also have been destroyed (sometimes all three). In this case it was D362 and D364. Repairs were simple - fit two new diodes and a new switching transistor. In place of the 2SC1046L I use a 2S0350 or a 2S0380. Both have higher ratings than the 2SC1046L and my pref- DECEMBER1988 63 SERVICEMAN'S LOG take some time to find the real fault. Fortunately, they had a spare set. Circuit checks So it was back to the bench. I connected the CRO to the switching transistor collector, hoping I might detect some abnormality to account for what it now transpired were five transistor failures in a few weeks. Unfortunately, this only revealed that the waveform was a copybook version of that shown on the circuit. At this stage, I suspected that something might be generating the odd spike or spikes but, unless I was very lucky, I wouldn't be watching when they occurred. In the light of this there was little I could do except let the set run and hope that when it failed again - as I felt sure it would - it would provide some clue. In fact, the set ran for several days with no signs of trouble. Then, one afternoon, I left · the workshop for a few minutes and returned to find it dead. I pulled the faulty transistor out, found a couple of the diodes which had gone with it, and replaced these as a matter of course. But there seemed little point in simply 64 SILICON CHIP fitting another transistor and waiting for it to fail in a few days. I had to make some effort to find the cause. More in desperation than anything else I decided to examine the heatsink mounting and the associated connections to the board, in case an intermittent connection might be generating spikes. So I unbolted it from the board and carefully inspected the mechanical assembly. I drew a complete blank; there was nothing to arouse the slightest suspicion. But the exercise did prompt another thought; what about the mica insulating washer between the transistor and the heatsink? The best view of it in situ revealed nothing so I pulled it out for a closer look through a jeweller's loupe. And there it was; what I had mistaken for a tiny spot of discolouration which often occurs in mica - was in fact a pinhole. It was so small that I doubt that more than the point of a pin would have passed through it. Well, we seemed to be getting somewhere at last. I fished out a new washer, examined it under the glass just to make sure, then fitted everything back together. The set came good immediately and I settled down for another soak test. Another splat It was a brief test. The set hadn't run for more than a couple of hours when there was a sudden "splat" and it went dead. My heart sank: not only had I not fixed the fault but I had probably done in another transistor. And these are not the 10-cent variety- they run closer to $10, even at trade prices. Closer examination brought some consolation; the mains fuse had blown, but the transistor and diodes were still intact. What was more, there was a clear mark where the flashover had occurred; from the transistor case (collector) to the heatsink, across the edge of the mica washer. And it was then that I realised that the new washer was smaller than the one it had replaced. Both were nominal TO3 washers but the original had been a good 5mm larger all round than the transistor case, while the replacement was a neat fit. I must confess that I was somewhat puzzled by this turn of events. Was the design so critical that only an oversize washer would withstand the normal voltages in this part of the circuit? There seemed to be only one way to find out; fit an oversize washer and try again. After some searching I found one; larger in fact than the original, being close to 8mm larger all round. So this was duly fitted and, muttering something along the lines of "Beat that, you b ... ", I switched on again. And again the set came up and played normally. For a couple of hours. Then there was another splat and this time it took out the transistor, plus one of the diodes. And again the weak spot was evident; the bolt holes in the washer were marginally larger than the previous ones and this was where it had flashed over. I was feeling pretty desperate ·1: ·ER.. UNIT I I ' C:307 RJO< 560 K c:i ,o CJII '"""' '"""' TC~'l9 '305 560K ,., i t C387 100., F . , ,,,'~ m -!- POWER-SUPPLY UNIT ':' ') OEFLl:"CTI ON Fig.1: the power supply circuit for the Sanyo Model CPT 6603 receiver. An obscure and frustrating fault caused repeated failure of the main switching transistor, Q361. and disheartened by now, but there seemed to be nothing for it but to heed the obvious lesson and try again. After a lot of searching I found a large washer with small holes, put everything back together and tried again. This time things looked a lot more promising. The set played for several days, during which time the lady customer was on the phone showing obvious signs of impatience. I explained that, hopefully, the fault had been fixed but that I wanted to run the set for a couple more days, just to be sure. Somewhat grudgingly, she accepted my explanation. So I ran the set for a few more days and then, with no hint of trouble, rang the lady and told her she could collect the set. And I did explain that I was making an additional charge - about $30 - purely to cover material costs - ie, the transistors. I would not have dared to try to charge for my time. She seemed to accept this and duly collected the set and paid the bill. I heaved a sigh of relief as the set went out the door. An irate customer It was a misplaced gesture. The set had been gone only three days before the lady was on the phone with the news that it had failed again. And, understandably, she was pretty irate. For that I could hardly blame her. From where she stood she had spent a lot of money (including whatever the other serviceman had charged), experienced a lot of inconvenience, and seemed to be getting nowhere. But what upset me was her threat to take the matter to consumer affairs; in fact, she intimated that she had already contacted them. Assuming that this was not just bluff, and knowing consumer affairs, I imagine that she would have been advised to take the matter back to me, then contact them again if I refused to co-operate. Since I had never had any such intention I wasn't particularly worried about the threat but I was an- noyed. I felt that she might at least have consulted me first. And I spelt this out, adding that I was perfectly willing to stick with the problem, at no additional cost, until it was solved. She calmed down a little after that and agreed to bring the set in again. Naturally it was exactly the same fault, except that there was no evidence of a flashover from transistor to frame. I'd beaten that but it was now clear that this was only a symptom. And it was also clear that I needed help. So I rang the Sanyo service department and eventually contacted a technician who seemed to be familiar with the fault. We had a long discussion and out of it came a list of components which experience had shown were likely suspects. These were: C361 (2200pF) in series with R361 between emitter and collector of Q361; diode D361; capacitors C332 (22µF) and C351 (220µF), connected to terminal 13 of the converter transformer (T361); and the main filter DECEMBER1988 65 Problems? . SERVICEMAN'S LOG ' .. ' . . •: ... and you don't have our I20page catalogue . .. .... .. I-\£~, ~INK At last . .. a TRADE catalogue for the consumer ARISTA ... your one-stop problem solver. Video plugs and sockets .. . Video extension speakers .. . Video flyleads . .. Video RF interference filters .. . Video splitters .. . Indoor antennas . . . Video switching units . . . Down converters . . . Video speaker controllers . . . Video camera lights . .. Video tape rewinders ... Video cine adaptors . . . Video head cleaners . . . Video splicing kits ... Video storage cases . . . Video dust covers . . . Video leads . . . Scart plug leads . . . Video dubbing kits . . . Video headphones . . . Video shotgun and wireless microphone systems .. . Pre-amplifiers with video inputs .. . Video camera stands . .. Just about anything you want. . . . Try us ... NOW! Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ARISTI\. ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 66 SILICON CHIP W~'S\½ER M\CA ~£'RE. WAS A G~~~ MARK ~~E 1ME: FLASHOVE."R \.\AD CXCOR~E.'t); FROM -rME -r'R.AN~\S"f"OR CASE. 1'0 "ffie. HEP«'SINK, AGRO~S 1'\E. E-'PGE 0~ 'THE MICA WAS\-\~,, ... capacitors, C310 and C311, both 100µF. But he'd kept the best bit until last. A prime suspect was the trigger transistor, Q321. This should be replaced as a matter of course, along with any othe~_r of the aforementioned components which tested less that 100% or were doubtful for any reason. I thanked him very much and then, as he wished me luck, he joked; "If that doesn't fix it, - you're on your own." A comforting thought! But at least I now had a few leads to follow. I started with C361 and D361. Both checked OK but I replaced them anyway; after all, if a minor component has to be pulled out to be tested, it is just as easy to fit a new one in its place . When I came to capacitors C332 and 351 it was obvious that these had been replaced by the previous serviceman. Not only were they brand new but, for once, I was grateful for his style of soldering; at least I knew what he had tried. Similarly, the main smoothing capacitors, C310 and 311, had obviously been removed, though I couldn't be sure they'd been replac- ed. So I pulled them out and checked them. They both tested OK, well on the plus side in fact, so I refitted them. That left only the trigger transistor, Q321. Since my predecessor seemed to have been following the same path, I wondered whether he had received the same advice and had replaced this also. If he had, we were back to square one. Fortunately one glance at the board reassured me. There was no way that Butcher Bill could have removed that transistor and put it back the way it was. So out it came and in went a replacement. Then I fitted yet another switching transistor, put everything back together, and switched on again. It was no surprise when the set came up with perfect picture and sound; that had happened many times before. The real test was whether it would last. I ran the set every day and all day for the next fortnight and it never missed a beat. But as vital as this test was, I couldn't convince the customer of that. In spite of the fact that they had a spare set, she was on the phone every couple of days wanting to know when it TETIA TV TIPS Kriesler 59-4/5/6 Telecommander Remote Control Symptom: At switch on will select channel 6 sound only at low volume. No picture . When any channel button is pressed, sound increases to normal but still no sign of picture . Cure: IC1320 {TDB1030) faulty. Although IC1380 does the channel selection , it is IC1320 that does the actual switching and a fault in this chip cuts off the tuning voltage. would be ready. And no amount of explanation on my part seemed to penetrate. But at the end of a fortnight I reckoned that the point had been proved, at least to the extent that it could ever be proved, and I returned the set to her. I made no charge and urged her to contact me if there was further trouble. This was accepted with moderate grace but without any enthusiasm. Well, that really is the end of the story, except that several months have now passed and I have checked the situation several times during that period. And each time I have been assured that all is well. So it would seem that Q321 was the real culprit. Of course it's easy to be wise after the event but it is now obvious that the flashovers around the transistor were merely symptoms of the fault that was generating destructive spikes. The fact that I fitted washers marginally different from the original simply served to produce a nice red herring; one which cost me dearly. So why did Q321 generate those spikes? I haven't a clue - and neither, it would seem, does Sanyo. Suffice it to say that it is a well documented fault and one worth noting. Perhaps this story may save someone else the run around. Another mystery And while we are talking about mysteries, here is another one to mull over. It is about a brand new National colour TV set, model AW A Thorn 3500 Series Symptom: Very low, wedge shaped picture with very bad convergence. All voltages normal and vertical output waveforms also normal. Looks very much like shorted turns in the yoke. Cure: Break in track on convergence board, between Plug 25 Pin 6, and L7 54. This track passes close to one end of R751, a known source of dry joints and the break was at the closest point to the resistor. TC2959, only recently released. This is a most impressive set, featuring a 74cm (29in) screen, a frighteningly elaborate remote control system, and a price tag of about $2000 to match. It also boasts the best picture resolution that I have ever seen on a colour set. Shortly after its release the makers issued a modification sheet concerning a corner purity problem. This was due to insufficient degaussing current due, in turn, to the type of degaussing thermistor originally fitted. It recommended fitting an alternative type, Part No. ERPF5BOM12OG. I have modified a few of these sets and the modification works well, even without any external degaussing. So I wasn't worried when one of my regular customers phoned to say that they were having trouble with this model set, the customer's description of the fault being that " ... the colour's gone all funny". She explained that the set had been working fine when they had gone away for the weekend but had "gone funny" when switched on after they returned. I imagined that it was just another modification job. In fact it turned out to be one of the worst purity problems I have ever seen; the whole screen was a bright random pattern involving every colour of the rainbow. There was no way that this was the problem I had anticipated. Nevertheless, I went through the motions of checking the thermistor, confirmed that it was the old type, Circuit Notebook ... continued from page 59 plugpacks up to 15VAC are suitable. Either way, the source should be able to supply about 50mA or more. The circuit operation relies on the fact that the LM317 maintains 1.25V (nominally) between its adjust terminal and the output terminal. By connecting a resistor between these terminals it can thereby be made to function as a precise constant current source which is independent of input voltage or load voltage. Two resistors in series, 22n and 2.20, set the constant current at close to 50 milliamps (actually 51.6 for a regulator voltage of 1.25V}. Up to six cells in series can be charged. Charging time is 14 hours (unless otherwise specified). If you have 400mAh AA cells they should be charged for 14 hours at 40mA. To set the ch.arging charging current at 40mA, change the 2.20 to 8.20. 116 TV TECHNICIANS & SERVICE COMPANIES Have your PHILIPS V ARICAP TUNERS (ELC2060) Repaired or Exchanged Only $17 .00 ea. Ten or more $15.00 ea. Quick Service 3 Months Warrc1nty T.V. Test Equipment Shorted Turns Tester (Silicon Chip, Sept. 88) $65.00 ·+ Tax Hi-Voltage Probe 0 · 50kV. $70.00 + Tax Send Faulty Tuners Cheques and money orders + P&P $2.00 or C.O.D. -:r.v.Tu IIERs) 216 Canterbury Road, Revesby 2212, Sydney Australia Phone: {02) 77 4 1154 DECEMBER 1988 67 presto! - the problem vanished; I had a first class picture with as high a degree of purity as I have ever seen. So what was going on? My first reaction was that there had to be some factor in the customer's home which I had overlooked, such as audio speakers which might have been moved close to the TV set. But even that assumption posed as many questions as it answered. In order to change the thermistor, I had pulled the set into the centre of the room, where it was quite clear of any other objects. So why, in that situation, had my degaussing wand lost its magic? Spurious magnetism and fitted a new one. All of which had no effect whatever on the problem. This didn't surprise me and I simply reached for the degaussing wand and gave the front of the set a once over lightly. But that didn't help either. When I switched the set on again the ef~ feet was as bad as ever, although I did get the impression that the actual pattern had changed. So I tried again, being more careful this time and since the back was still off the cabinet, I went right over the inside, poking the wand in wherever it would go. Still no joy. I went through the ritual several times but seemed unable to make any impression. The only noticable effect was that, if I left the set running, I could observe a changing pattern but with no hint of reduction. Faulty picture tube That really rocked me. There was only one possible explanation in my experience and that was a faulty picture tube. The fault is rare but I have experienced it. It is caused by a faulty spot weld securing one corner of the shadow mask, allowing the mask to move back and forth and upset the critical adjustment of the whole system. And a 68 SILICON CHIP symptom is that any attempt to degauss the set simply changes the pattern. It was also a situation which called for some diplomacy. The people involved were very understanding types but I hesitated to suggest that their brand new $2000 set had a faulty picture tube. While it would be fixed under warranty, they'd probably worry about a picture tube failure for years to come! So I simply suggested that the fault needed workshop attention for a few days. They still had their old set, a Philips K9, which would serve in the meantime. And so the set finished up in the shop. I left it for a couple of days, partly to think about the problem and partly to organise a discussion with the National service department. It was just possible that they may have already encountered a problem with this picture tube. But when I put it to them I drew a blank. While they were well aware of such a possibility, they had not had any such problems. So I was on my own. At the first opportunity I gave the set another try. It displayed exactly the same pattern as before and, on an impulse, I gave it another once over lightly with the wand. And Nevertheless, I rang the customer and asked her whether there was such a speaker system and whether it might have been moved close to the TV set. Yes, they did have such a system and one speaker normally sat alongside the TV set. In fact, it had been sitting there when I called. I realised later that if it had had a mouth it would have bitten me. I was just too intent on the TV set to notice it and, as I said, I had pulled the set clear anyway. More to the point the lady was quite adamant that nothing which might be involved had been changed. The set was working perfectly when they left the house on the Friday night, the house was empty until they returned on the Sunday night and, at first switch-on, the set was faulty. There was nothing for it but to return the set to the customer and test it in its original environment. The answer - nothing. Nothing untoward, that is. The set behaved perfectly, even though I had taken the trouble to ensure that it went back exactly where it had been, relative to the speaker. Finally, I moved the speaker all around the set and did everything I could, short of shoving it inside the cabinet, to create the fault. Nothing worked; nothing I could do would re-create the problem. And the set has been running for many weeks now with no hint of trouble. So the mystery remains. Any ideas, anybody? ~ AMATEUR RADIO By GARRY CHATT, VK2YBX Build this simple adaptor to receive SSB on shortwave AM receivers This project is about as simple as they come. It's a 455kHz oscillator that will allow you to receive SSB signals on your AM-only shortwave receiver. +5V OUTPUT 1M 100pF J 100pFl Fig.1: a ceramic resonator is used in a CMOS oscillator circuit to give a 455kHz source. build and will convert your AM shortwave receiver to SSB reception. AM & SSB signals The parts for the 455kHz oscillator can be mounted on a small piece of Veroboard. To demodulate an SSB signal, you simply wrap the output lead several times around the receiver and tune for best quality audio. Most experienced amateurs know that SSB (single sideband) reception requires a receiver fitted with a "product detector" or BFO (beat frequency oscillator) to reinsert the missing carrier. They also know that such receivers command significantly higher prices than AM only models. It's also a fact that signals broadcast using SSB tend to be far more 70 SILICON CHIP interesting to amateurs and shortwave listeners than the standard HF broadcasts, such as Radio Australia, the BBC and the VOA (Voice of America). The problem is, most readers only have a standard AM shortwave receiver - one that's incapable of SSB reception. This simple circuit solves that problem. It uses only a handful of parts, will cost you less than $5 to To understand how the adaptor works, it is necessary to explain the basic differences between AM and SSB transmissions. A modulated AM signal consists of a carrier and two symmetrically spaced sidebands (see Fig.2). As can be seen from Fig.3, the amplitude of the carrier is a function of the amplitude of the modulating signal. The two sidebands on either side of the carrier have the same amplitude (Figs.2 & 4) and carry the same information. This is why AM is also sometimes referred to as double sideband, or DSB for short. In fact, the carrier itself conveys no information. In mathematical terms: AM power = carrier power + sideband power = Pre + P(fc + fmJ + P(fc - fmJ· Fig.2: the amplitude of an AM carrier is a function of the amplitude of the modulating signal. Fig.5: you can use an oversize drill to cut the tracks on the Verohoard. How it works AMPLITUDE le-Im le le+lm FREQUENCY Fig.3: a modulated AM signal consists of a carrier (fc) and two symmetrically spaced sidehands (fc - fm and fc + fm). AMPLITUDE The heart of the circuit is a Murata "Ceralock" ceramic resonator. This provides a reliable 455kHz source at a fraction of the cost of a crystal. The resonator is used in the CMOS oscillator circuit shown in Fig.1 and provides an RF output level of 5V peak-to- peak. The output of the oscillator is then fed to a length of insulated hookup wire which is wrapped several times around the receiver, thus providing a degree of inductive coupling. The amount of signal required varies from receiver to receiver and can be adjusted by varying the number of turns. Construction (fe-lmmaxJ (fe-lmmin) le (fe+lmmin) (fe+lmmaxJ FREQUENCY Fig.4: the two sidebands on either side of the carrier have the same amplitude and carry the same information. By removing one sideband and the carrier, more efficient use of the available transmitter power is made without sacrificing the transfer of information from transmitter to receiver. In fact, an SSB transmitter uses approximately one quarter the power of an equivalent AM transmitter. Another advantage of SSB operation is that the bandwidth required to transmit the signal is significantly reduced. So, by removing the carrier and one sideband, we can make more efficient use of the RF spectrum. Receiving SSB To demodulate an SSB signal (ie, to turn it back into intelligible speech), it is necessary to insert a locally generated carrier at the receiver. This carrier can be generated by using an external oscillator tuned to the receiver's intermediate frequency (IF) - in this case, 455kHz. The new carrier provides a reference frequency against which the upper or lower sideband can be demodulated. Note that the opposite sideband is also generated during this process, so that a complete AM signal is available for detection. OK, so that's how we convert an inexpensive shortwave receiver to SSB operation. It's an arrangement that can be made to work quite well but don't expect it to perform as well as a fully-fledged SSB receiver with narrowband IF stages and special audio filters. The unit can easily be made up on a small piece of Veroboard. Fig.5 shows the wiring details. You can make the cuts in the tracks using an oversize drill. Note that all unused input and output pins on the 4069 are grounded to prevent spurious oscillation. The recommended maximum supply voltage when using the CSB455E resonator is 5 volts. If portable operation is contemplated, the unit could be powered from a 9V battery via a 5V 3-terminal regulator. Because the ceramic resonator operates at a fixed frequency, no tuning of the circuit is required. To demodulate an SSB signal, first tune your AM radio to the SSB signal (it will sound very distorted). You can then wrap the oscillator output lead around the receiver, apply 5V, and carefully tune your receiver for best quality demodulated audio. Footnote: the CS455E ceramic resonator is available from Dauner Electronics, 51 Georges Crescent, Georges Hall 2198 . Phone (02) 724 6982. DECEMBER1988 71 NTAST EWSTOR ARRAMATT Jaycar has opened a much LARGER \, new store at Parramatta. We had to reluclantly close the Carlingford store as It was simply too small for~ our operation. We sincerely thank our~ Carlingford regulars for their patronage over the past 7 years. Carlingford was our first branch store and holds great memories for us. Carlingford customers should welcome the LARGER PREMISES 10 minutes down Pennant HIiis Rd to North Parramatta Parking has VASTLY IMPROVED. Don't forget ,to call in and see Troy's familiar f;,.ce. We look 7 forward to being of more efficient<at> service to youl 355-357 Church Street Parramatta PHONE: (02) 683 3377 , -~ t ~ lf/< Buy a WELL PROVEN famous AVTEK Muttimodem and save a bundle. This stock will not be replaced and FIRST BUYERS ONLY will benefit. Multimodem Autoanswer II • BELOW COST • Vlatel COIT1)atlble, 1200f75 Baud, CCITT/Bell standard. Cat. XC-4822. Sold originally for $349, we have reduced to $199, A FEW LEFT at $125 auantitieslimitedsobequick. Mini Modem II • BELOW COST • Viatel, 1200f75 and 300/300. can be powered by a computer directly, e.g. MlcroBee. Includes power supply. $99 • BE QUICK Cat. XC-4825 MegaModem Model V21, V22- Hayes "Al" corrpatible intelligent unit. A few only at this price. Cat. XC-4850 WAJ ~E~EMBER ONLY $250 Merry Christmas ONIC ANVIL!!! QUALITY JEWELLERS SCREWDRIVER SET yist. Hammer that IC into r anvllll Weighs 2.7kg Cat. TD-2040 Size 180mm long BOmmhigh Quality easy to use colour coded screwdriver set with swivel plastic heads. Screwdrivers include slotted 1.0, 1.6, 2.4, 3mm Philips No. 0, 1 Supplied In transparent plastic case. Cat. TD-2005 . 7" $5.95 X 5" met Grab a packet of these! Pack ol 100 plated U-shaped staples with soft-nylon saddle, you can hammer them In to wood, particle board etc. Nylon saddle cushions the wiring. Ideal for burglar alarms, speaker flex, TV coax etc., and NO expensive staple gun needed! at. AS-3035 NLY $2 ea ~:.:~~~~-ultab; ;~; AVE$6 Bargain 1: 1.25V MES lenshead globes. Ideal for single cell torches . ,. ,4 USUALLy soe ea 25 for $2 (only se ea) 100 for $6 (only se ea) 1'j Bargain 2: 5 volt MES torch globes. Works OK on 6V. ~ soe ea A.,e.,; ~ !P' Bargain 3: 12 volt BC car replacement globes suit tail lights, blinkers, garden lights, etc. 1r USUALLY ABOUT $3 ea 2for$1 ~~ / ~ Bargain 4: 6 . 3 Vglobes ~MES Cat. SL-2662 USUALLy soe ea . 4 for $1 .· · 10 for $2 · · · 100 for $15 Cat. SL-2654 Limited quantities on all globes. metal black grill. Cat. AS-3036 ONLY $3 ea SAVE $7 Cat. SL2660 USUALLy 10 for$1 Insulated Staples No Staple Gun Required You would expect to pay about $8 for the 7 x 5 and $10for the 9 x 6 nornmally. ...C _ ar __B_o_n_n_ e_t______-1 Loc king DeYice This device will lock the Bowoen Cable (i.e. the 'wire' that goes between the bonnel release handle and the bonnet catch) AUTOMATICALLY when you switch your car alarm on. The unit will give COMPLETE under-bonnet security! The locking device includes solenoid lock, control box, emergency Bowden cable release, screws, connector bracket and other hardware for univers;,.i fitting. Instructions supplied. Cat. LA-5400 A BARGAIN A T ONLY $19.95 WOULD NORMALLV COST ABOUT $70 $13.95 30 PIECE ENGINEER'S DRIVER SET At lastl A driver set incorporating those obscure shaped headsl Have you flVer needed recently to service an electric tool? Chances are you would not have been able to do so because the screws holding the appliance together had strange shaped he;,.ds. Well now you can with our 30 piece driver sell This sel contains all the driver bits you are EVER likely to encounter (See Below). Basic to the set is an 8 1/2" Chrome-Vanadium driver which will accept any of the 28 hardened steel bits supplied. They are held into the sockel of the driver by a small magnet - so you can use the driver in any position. The screw-together hollow handle will hold several tips so you don, havetotakethe.wholesetwlth you into the field . There is a tip here to suit ;,.Jmost any screw/nut you may come across. ankerflex, MEDIUM SIZE: Suitable for 3C-2V or RG58 coax and heavy speaker flex. Cat. HP-1186 $2.00 Here's what you get: • 5 Slotted Bits 0-1, 3-4, 5-6, 8-10, 12 • 5 Hex Bits 3132", 5/64", 7/64", 1/8", 9/64" • 4 Philips Bits No. 0, 1, 2 & 3 • 4 Square Recess Bits No. 0, 1, 2 & 3 • 6 Ton< Bits T10, T15, T20, T25, T30, T40 • 2 Pozldrive ·Bits No. 1 & 2 • 1 x 1/4" Drive Socket Adaptor • 1 x 1/4" Drive Hex Bit Holder And its all housed in a sealable tough plastic case WI DERANGE MAGNAVOX BJX $31.50 The SJX is as· twin cone speaker suitable for medium power handling applications. SPECIFICATIONS 40wans RMS Power Handling Resonant Freq. 44Hz to - 12kHz Freq. Range 93d8 Sensitivity Cat. CE-2333 WOOFERS MAGNAVOX SW The SW Mk6 is a high fidellty woofer. SPECIFICATIONS Power Handling 65 wans RMS Resonant Freq. 43Hz to - 5kHz Freq. Range Sensitivity 96d8 Cat.CW-2109 MAGNAVOX BWR $36.50 The BWR is a high fidelity wide range twin cones· driver. SPECIFICATIONS Power Handling 65 wans RMS Resonant Freq. 43Hz to - 12kHz Freq. Range Sensitivity 96d8 Cat. CE-2338 JAYCAR FOR MAGNAVOX SPEAKERS MAGNAVOX 12W MAGNAVOX 10W 12" woofer, medium power, low cost, high The 1ow is a 1o· high quality, high power, medium price woofer. SPECIFICATIONS Power Handling 75 wans rms Freq. Response 30Hz - 5,000Hz Resonant Freq. 33Hz Cat. CW-2118 $43.50 $39.50 IIIIAGNAVOXBMV 8/30 Replacement If you own a pair of 8/30 woofers, you can now easily update them. Your old 8/30's handle 30 wans rms, the new BMV's handle 120 watts rms. No need to buy new cabinets, SMV's mount in the same hole, otherwise it's a high quality, high power 8" woofer for most applications. SPECIFICATIONS Power Handling 120 wans rms Resonant Freq 31Hz lo - 4kHz Freq. Range Sensitivity 96d8 Cat. CW-211 0 MAGNAVOX12MV The 12MV is a high power high fidelity woofer. SPECIFICATIONS Power Handling 150watts rms Resonant Freq. 19Hz Freq. Range to - 3kHz Sensitivity 96d8 Cat.CW-2125 $99.50 POLYPROPYLENE MAGNAVOX WOOFERS JC 150 6" WOOFER SPECIFICATIONS Resonant Freq. Sensitivity Power Handling Freq . Response Cat. CW-2105 49Hz 95dB 50 wans nms 80-BOOOHz Easy to use automatic connectors. Simply wrap around the existing wire and new wire and squeeze. NORMALLY $1.25 for 4 or 31~ ea (Two styles supplied in pack) PACK 15 for $1.95 (only 13e ea) Cat. HP-1207 PACK 100 for $10 (only 1oeea) Cat. HP-"1208 quality. 25mm voice coil wound on aluminium former. Polyurethane foam roll surround. SPECIFICATIONS Power Handling Freq. Response Resonant Freq . Cat. CW-2 122 $56.50 ULTRASONIC PEST & INSECT REPELLERS • Frequency range 30kHz to 65kHz variable • Output level 130dB • Both units include 240V power adaptors ~fflil.l! Single Transducer ONLY $29.95 SAVE $10 WAS $29.50 NOW $17.95 SAVE39% SASSO Mylar drivers, freq. reponse DUAL TRANSDUCER ONLY $39.95 WAS$59.50 NOW $39.50 SAVE 34% For full details see our catalogue. 20Hz-25kHz . Quality muff pads. Cat. AA-2022 Cat. YS-5512 WAS $39.50 CAR NEGATIVE ION GENERATOR Now you can have all the benefrrs of your home ioniser in your car. This great new Jaycar direct import is durable, stylish and compact, measuring only 110mm in total length . It simply plugs directly into the cigarette lighter socket in your car. It can generate large amounts of negative ions for purifying air, and some ozone for eliminating odour. Jaycar's direct importing cuts out the middle man and saves you money. ONLY $34.95 NEGATIVE ION GENERATOR iii GREAT XMAS PRESENT TO YOURSELF We are holding small stocks of BRAND NEW valves going back to the A~ l EMS - · liquidate this current rrodel rrerchandise. ONCE AGAIN their staggering loss is YOUR GAIN. OFFER No1 SAVE AROUND $200 Genuine NADY MODEL 201GT Guitar wireless microphone link which includes FM "True Diversity" receiver, bodypack transmitter with high impedance input (suitable for guitar pickups, bass, sax, etc). The body pack accepts a standard 6.5mm plug and the audio lead acts as the antenna. neat! The body pack measures 96x60x203mm and weighs only 70 grams. It requires a 9V alkaline battery. Both transmitter and receiver are crystal locked and offer 20-20,000Hz ±3dB frequency response and 120dB (max SPL A-weighted) dynamic range. Output is line level 600 ohms. Minimum adverse operating range 200 feet, line-of-sight 1500 feet. Elsewhere you will pay $800+ for this system in Australia. But, while they last you will be able to get this product from us for only $5991 That's right, you WILL SAVE around $200 over the normal price in Australia (Australian rec retail $799). (If more than one is ordered they will be supplied on separate frequencies. Cat. DT-5020 $599inctax OFFER No2 SAVE AROUND $300 Genuine NADY 201 HT microphone wireless system comprising of YD-04 microphone (virtually identical per1ormance to Shure SM-55), Integral antenna (no dangling wires) low battery ligh1 and professionally rugged. Measures 222(L) x 36(Dia)mm weighs 232 grams. Use 9V cell. Included of course is the 201 "True Diversity" receiver matched to the same frequency. System performance and range are similar to 201GT above. (You see this system used by TV tertainers in the US all the 1imel) (If more than one ordered or 1 x 201GT and 1 x 201 HT ordered they will be supplied on dttferent frequencies.) cat. DT-5030 N.Z. Customers save further 150Yo on these Aust. prices! DT-5020 $463 tax free DT-5030 $543 tax free SAVE 38% Vintage Valve S ale GENUINE ~ ~ FM DIVERSITY WIRELESS MIC/ GUITAR LINK SELLOUT You would DIE if you knew where we bought this shipment of brandnew genuine USmade NADY wireless PA gear from! Suffice to say that they lost a fortune to NOW $24.50 .. ••· . . .:__ ~, _, . , . . . . . Don't forget Carlingford Store now moved to Parramatta 355 Church Street Phone (02) 683 3377 240 VOLT - SAVE $50 Cat. YX-2905 • t $ 699 lnC ax Top of the range, excellent sound. Quality phones. Cat. AA-2023 Features Mylar drivers, sponge earpads, metal 3.5mm stereo plug. Cat. AA-2021 Cat. YS-5510 SPECIAL INTRODUCTORY OFFER DIGITAL STEREO HEADPHONES SA888 p&p fixed cost $20/unlt ~::ra~~ob:r;~!nt types are available but most are in very small quantities. Stock will not be kept at local stores it will have to be ordered in for you against pre-payment. This does not guarantee that the stock may have already been sold. All the valves are one price $5 ea. If sold out money refunded in full. Stock is new but NO WARRANTY is offered. Normal mail O.K. See list of part numbers: 6FC7-SBY7-SCG7•6CK6•6CHS-6AU5Gl•6BJ6 •6AN8A•6BA8A•3V4•1 R5•1 S5•6AL3•6AK8 •6BMS-6EM7•6SA7GT-SBH8•6S2•6CM7•5AS4 •6BX7GT-SBW7•6BS8•6BN6-SB R5•6BK7B •6BJS-6BJ7-SBFS-6BE7-SABS-6AC7•6AH4GT •6AB5•6A6•6AB4•6AG5•6BD6•6BD5Gl•6BC8 •6AU7-SBC9Cr6AS8•6AQ6•6ANS-6AS5•6AQ7 •25Z4G-2SZ5•12ATS-UF41•9AO&12AS-117Z3 •9AKS•6YSG-7AN7'12AUS-12AX4GTB•12BD6 •12BV7•12BA7•1207GT•12K7GT•12SA7•12SG7 •12SO7GT•12SN7•12SK7GT•15A6•21AS-16A5 •15DQ8•6SC7•6AU4GT•6S R7•6SH7GT •6CD6GA•6CDS-6BO6GT•6DB5•6DA5•6DE6 •6DS8•6ES6•6EV8•6ET6•6C6•6B27•6CF6 •EC86•6CM4•6CQ6•6DA4•6N3•6J N8•6G6 •6F8G•6W6GT•6R7•6N7•UCH21•UCL83'UY1 N •UCH42'UCH41 • 1AB& 1A& 1A5GT• 1ABS-PCL83 •UBL21 •EM87•PGL83•DL93•3A5•3A4•3Q4 •3O5GT •5GK3•E R4GYB•5U8• 1D7G• 1DBGT • 1F6•35C5•50ENS-32L7GT •C8•C1 •6AN8A •6BH8•6BVB• 12AC.5•12AN7•6AW8A•6AD8 •6EH7•6BQ6GTB•6BQ7A•6BZ6•6AB8•6BF5 •SAM 5•6CM 7•6BH8•6B U8•6AT6•6AD8 •6EM5•6EB8•6V9•6X2•6W6GT•6N8• 12AA6 •12BAS-12BE6•6U8•6CW7•6CD6•6DQ5•CB 1C •CF1 •CY31 •6CD6GA ALL ONE PRICE $5.00 each Machined Aircraft Grade Aluminium Flash light What an excellent product! It measures 145mm long and runs off 2 - AA batteries. It is 70 times brighter than a normal torch and the beam is adjustable from spot to beam, and it's waterproof &nd shockproof. Durable anodised abrasion resistant finish, with a non sl~ knurled grip. This torch will last a lifetime. Small enough to fit inside a car glovebox or handbag. It can also be used as a lantern. Unscrew the top and the bulb is exposed to give 360° light. We have seen these torches for $19. We have direct imported them and can offer them for the amazing price of only $9.95. Spare bulbs available for only $1 .50 (Cat. ST-3002) Cat. ST-3000 ({--- ONLY$9.95~ Quality Stacking Banana Plugs • NEW RANGE OF COLOURS I • NEW LOWER PRICES! RED BLACK GREEN BLUE YELLOW Cai. Cat. Cat. Cat. Cat. PP-0390 were $1.95 PP-0391 were $1.95 PP-0381 PP-0382 PP-0383 10+ $1.10 ea ONLY $l .2S ea THE LATEST KITS 120WAITPA/ GIDTARAMP MODULE Ref: Silicon Chip November 1988 This rugged Mosfet amp module is designed specifically to drive a 100V line transformer for PA. It can also be used for guitar and stereo amps, Short form kit. PC board and all components supplied, including Mosfets. No power supply parts or heatsink included in kit. Heatsink extra Cat. HH-8550 $22.95 Cat. KC-5043 (kit) OUR MOST POPULAR KIT IN 1988! FM Stereo Transmitter ''MINI MIITER" CAR SAFETY LIGHT Ref: Silicon Chip October 1988 This fantastic project enables you to transmit a signal IN STEREO over the FM band. The range is limlted to about 20 metres or so, so it's not a nuisance to anyone else. It uses a single 1.5V M (penlight) cell which lasts for ages. Just imagine I You can listen to your CD player on your FM headphone receiver while washing your earl You can play your Walkman CD player over your car stereo - no wires I The possibilities are endless I Set up your own micro FM Radio Station I The Jaycar kit of this project includes the hard.to get Rohm BA1404 chip and the CORRECT 38kHz crystal - even harder to getl All other specttied parts are included as well. Cat. KC-5041 Ref: Silicon Chip November 1988 Is your car in danger of being sideswiped at night? This project detects an approaching cars' headlights and'automatically turns on the brake lights to warn the driver. The brake lights switch off 5 seconds after the car has passed. Circuit is disabled during the day. Quallty Philips LDRs supplied Cat. KC-5044 $29.95 $72.50 $29.95 POWERMATE2 "KNIGHTRIDER" LED SCANNER Ref: Silicon Chip November 19:JB Provides the scanning effect same as on kit car In Knightrider TV program. Use for burglar alarm applications, novelty applications on kids toys, etc. PC board and all components supplied. Cat. KC-5042 Refer: EA October 1988 Revamped version of original Powermate power supply. Delivers clean, crisp regulated 13.8V DC at up to 5 arrps. Full kit. Ref: EA November 1988 Low cost 4 digit timer which can measure imervals from a few microseconds to hundreds of seconds. You can measure the speed of a slug from an air rifle, gott ball speed, etc. Short form kit, no box o, front panel supplied. Cat. KA-1708 $119 STROBOSCOPIC TUNER KIT Ref: EA July 1986 Cat. KA-1707 This simple circuit provides crysta~locked accuracy for tuning virtually any musical Instrument. It also doubles as a stable frequency reference tt you prefer to tune up by ear. Kit includes box and all parts. Cat. KA-1706 $59 $17.95 HANDS FREE TELEPHONE HEADSET $16.95 WIRELESS DOORBELL Ref: Silicon Chip August 1988 What a great idea. A wireless doorbell with the option to have as many sounders as your house requires. Transmitter is mounted in a UBS Jiffy box with a pushbutton switch which mounts outside your front door. Powered by a 9V battery. Receiver mounts in plastic box and requires 12V DC plugpack, our MP-3006 will do $14.95. Use as many receivers as you require. TRANSMITTER KIT RECEIVER KIT $47.50 So new, we don't even have a picture yet. As used with the Silicon Chip speakerphone project. Headset, microphone with lead and 3.5mm plug. Mini size ultra lightweight. Cat.M-2018 ' SPEAKERPHONE Ref: Silicon Chip Sept 1988 High quallty hands free telephone adaptor that works extremely well. Full kit including box, panel, isolating transformer and all parts. Cat. KC-5040 ONLY $89 PLAYMASTER/JAYCAR 60/60 BLUEPRINT AMPLIFIER Standard version still available Cat. KA-1652 $369 Cat. KA-1650 See our catalogue for full details 3_2_9___ _ _ _ _ ____ L...$,.__ Ref: Silicon Chip November 1988 Ideal for those who want to experiment with plasma displays. This kit is basically just the power supply. You can use a 240V globe anywhere up to 300 watts. (Warning with this unit you can not touch the globe whilst it is operating). Features adjustable display. Kit includes PCB, EHT transformer, box and all components, but not globe and holder (which are readily available). Cat. KC-5045 $75 UPGRADEDS000BLACK MONOLITH POWER AMP RE-BORN WITH TOPOLOGY MODULES Cat. KE-4200 $499 HEAD OFFICE MAIL ORDERS POST & PACKING 137 rrrr•~!_i_i_i_2_f_J_)~:~:~~~;_:_:_:_:_:_:_ _ _ _ _~_t_{_~_1_l_?_~-~~l-~~;-~_:_~_:~__ _M.:~~, ff VISA 1 i_:_R$_1oo_~_f_H__iJ_oi_:_ _ MAIL ORDER VIA YOUR ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY - CITY 117 York St. (02) 2671614- GORE HILL 188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 Mon-Fri 9 - 5.30 Sat 9 -4pm PARRAMATTA BURANDAQLD 144 Logan Ad (07) 393 0777 Mon-Fr, 9 - 5.30 Thurs 8.30 - Sat 9 - 12 __E ' ::::;;:LE Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Cl'uch SI (Cnr. Vtctoria Rd) (02) 683 3377 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 2pm 115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sat 8.30 -12 MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030 121 Forest Rd (02) 570 7000 Mon-Fri 9- 5.30 Thurs 8.30 pm - Sat 9 -12 SPRINGVALE VIC Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - ~ THE EVOLUTION OF ELECTRIC RAILWAYS In the space of about ten years or so, diesel electric locomotives completely displaced all the hundreds of thousands of tried and proven steam locomotives that had served well for one hundred and twenty years! Why? By BRYAN MAHER Herr Doktor Rudolph Diesel (Germany, 1858-1913), inventor of the internal combustion engine which now bears his name, envisaged a simpler and more efficient engine than the system pioneered by fellow German Karl Benz in 1878. The 76 SILICON CHIP diesel engine needs no electric spark nor carburettor, only a piston, cylinder, two valves and a pump to inject fuel oil under high pressure. When the piston has drawn air into the cylinder and compressed it to a high pressure and temperature, a small quantity of fuel oil is injected to cause self-combustion. This drives the piston down and turns the crankshaft. Herr Diesel originally intended his design for airplane propulsion but his first successful engine in 1897 was too heavy to fly. Consequently he turned his thoughts to diesel ship propulsion. His engine was more efficient than some of the reciprocating steam engines in shipping use at the time. Sadly his life was cut short, for he died in mysterious circumstances in 1913. After boarding a ship bound for England he apparently disappeared en route and was never seen again. It was before the outbreak of FACING PAGE - AMTRAK'S TURBOLINERS represent a blend of American and French design with their modern lines and comfortable interiors. Seven of these red, white and blue "turbos", built by Rohr Industries in California, are used on inter-city rail services. The photograph above shows an early NSW SRA diesel-electric passenger train. These trains were used on NSW country routes but have now given way to the recently introduced XPT. World War 1 and he might have been walking a political tightrope, as his 4-stroke diesel engine had potential for naval ship propulsion. The four "strokes" of his engine piston are air intake, air compression, power (fuel burning) and exhaust. Thus power is delivered on only one piston stroke out of each four; ie, one quarter of the time. Later Sir Dugald Clerk of England extended the diesel design to give one power stroke every time the piston travels downwards and one compression stroke on each upward movement; ie, one power stroke out of each two. This is called the "2-stroke" principle, which gives power one half of the time. Compared to a 4-stroke engine, the 2-stroke design gives more power for a given size and weight but its efficiency and fuel consumption may be greater or less depending on the construction. Since those days the diesel engine has pervaded every area of the transport industry, some ships today having engines so large that you would climb up two flights of stairs to go from the crankshaft floor to the cylinder head level. Their pistons can measure a metre in diameter and have a piston stroke of two metres. First diesel electric In 1913 the Mallesta and Sodermanlands Railway Company of Sweden made history as the first railway to use diesel electric propulsion regularly. But because diesel oil was scarce in Europe and hydro-electric power available, the Swedes retained their preference for electric railway traction. Today in Sweden there are only 533 diesel electric locomotives compared to 726 electric locomotives. But that little Swedish experi- ment did not go unnoticed on the other side of the world. In the USA the motor car and truck firm General Motors (GM to most people) had observed the advantages of diesel electric railroad propulsion and thought well ahead. We remember that in the period 1900 to 1930 the American steam locomotive had grown from 100 tonnes to over 500 tonnes, featuring designs with up to 24 driving wheels, such as the Erie Railroad's 2-8-8-8-2 monster built by the Baldwin Locomotive Works in 1914. The Mallet type loco itself weighed 384 tonnes and had an enormous tender carrying 37,850 litres of water (37.85 tonnes) and 16 tonnes of coal. This loco featured six steam cylinders each 91cm (3 feet) in diameter, working in compound with a boiler pressure of 1448 kilopascals (210psi). The tractive effort exerted was 72.7 tonnes. DECEMBER1988 77 AMTRAK'S "MINUTE MAN" HEADS for Boston on its way from Washington, near Warwick, Rhode Island. Although the Northeast Corridor is electrified between Washington and New Haven, diesel-electric locomotives are used the rest of the way to Boston. To ensure crew safety, the windscreen is bullet proof and can withstand the impact of a concrete block at speed. More powerful still was a 2-10-10-2 articulated steam locomotive built by Baldwin for the Virginian Railroad in 1918. Its largest cylinders were 1.22 metres (4 feet) in diameter and when all cylinders were fed with full steam pressure at 1483kPa (215psi) this locomotive produced a tractive effort of 79.38 tonnes (175,000lbs). Would you believe that it was the enormous power and tractive effort produced by these monster steam locos, the largest ever built, which produced the decline and death of the steam locomotive worldwide and the rise to dominance of the diesel electric locomotive? If you find that that strains credibility, consider if you will the following sequence of events. Single large locomotives American Railroads could be divided into the coal carriers (Virginian, Erie, Norfolk & Western, and 78 SILICON CHIP Chesapeake & Ohio Railroads) on the eastern side of the country and the long-haul freight carriers (Union Pacific, Santa Fe, etc) whose tracks crossed the western Rocky Mountains to the Pacific coast. The eastern coal carriers naturally leaned towards steam locos as coal and water were near at hand, tenders could be refilled often and their routes were not too long. All the eastern coal lines had to surmount the Appalachian and Allegheny mountains of Virginia and West Virginia on their way to the Atlantic Ocean export ports of Chesapeake Bay. Their monstrous locomotives single-handedly hauled coal trains of 7000 tonnes up the mountains on 1-in-62 grades and dragged 15,000 tonne trains on the coastal plains to the ports. But why not use two smaller locomotives in double-head mode? There were two reasons: (1) the difficulty in synchronising the starting of two huge steam locos; and (2) the cost of the extra loco crew of three (driver and two firemen). This led to the concentration on single huge locos. In contrast, the long-line freight railroads such as Union Pacific had to carry coal (and even water) thousands of kilometres to their locorefuelling points. In 1942, Santa Fe were hauling more than 200 large water tank wagons daily to quench the thirst of their steam locos running between Winslow, Arizona, through Flagstaff to Barstow, California. Thus in America the western Rocky Mountains were crossed by beautiful steam locomotives, each with a tender as big as a ship in tow. The 6000hp (4.5MW) "Big Boys", the largest Union Pacific steam locomotives, had a tender carrying 32 tonnes of coal and 110 tonnes of water. Two 16-wheel bogies were needed to support the nearly 200 tonnes of the tender. Australian inland railways had the same problem. Many a reader will remember outback steam passenger trains which included a large water tank truck immediately behind the loco tender. The Australian National Railways by necessity carried huge quantities of water between Port Pirie and Kalgoorlie. The classic steam loco used to cross the Nullarbor Plain was a copy of the NSW 36 class but with an oversize tender which weighed more than the loco! Such a line was ripe for the diesel electric salesmen! Enter diesel electrics Herr Doktor Diesel's first effort at rail traction in 1913 was a failure because he attempted direct drive from the engine to four coupled wheels. His 4-4-4 locomotive ran but was unpopular. The Swedish idea, pioneered by ASEA, used the diesel engine to drive a DC generator which powered electric traction motors, giving better control of speed and starting. By 1924 the first diesel electric loco appeared in the USA. Though only 300hp (334kW), this yard switching loco built by American General Electric Company was the beginning of an era. The world's first diesel electric loco for export was also produced in 1924 but it came not from the USA. It was an ASEA 200hp (149kW) Bo-Bo locomotive exported to Tunisia. It was a great success. In the same year both Austria and Germany were experimenting and Brown-Boveri/Fiat built a 440hp (328kW) diesel electric for service in Italy. In 1933 Germany had a diesel electric "Flying Hamburger" train running between Berlin and Hamburg. It covered the 285km in two hours eighteen minutes, averaging 123km/hour. Still, American railroads had steam hauled trains that ran faster. For example, the Santa Fe had to run some trains at 160km/hour to keep to timetable. So why did diesel electric traction demolish the steam locomotive? TWO POWERFUL CONRAIL Bo-Bo diesel electric locomotives are shown here hauling a heavy freight train. Each loco is an EMD Model GP9 weighing 114 tonnes and rated at 1.3MW (1700hp). The diesel engine is a 16-cylinder Model 567C which is direct-coupled to a DC generator. Cost comparisons Was the answer prime cost? No, not at all, for the big American manufacturers, like the Baldwin Locomotive Works, could turn out three steam locomotives per day, each costing only one third that of a diesel electric unit of equivalent power. Perhaps readers think that the cost of servicing a dirty steam locomotive for each 1000km run was more than the cost of keeping a diesel electric on the road? Not necessarily so. Many countries, including Australia, serviced their old steam locomotives in ancient, ill-equipped running shops. In 1940 it was still a practice at Eveleigh shops in NSW for candles to be used for illumination when lubricating the valve rods between mainframes in 50-class steam locos. Contrast that with the modern Norfolk & Western Railroad running shops in the USA which could service a 500 tonne giant steam locomotive and have it out on the road again in 50 minutes. And that included a complete clean, lubricate and refuel job, including cleaning inside the smokebox. It was entirely unrealistic for Australians in 1950 to compare the maintenance cost of a NSW 50-class steam freight locomotive, then 60 years old, with the 40-class diesel electric, in those days the latest thing on twelve wheels. The 40-class of 1650 hp (1.23MW) lasted about thirty years, about half the life of many steamers. A further complication arose with these diesel electrics: an instruction was issued that should they ever suffer a simple derailment, the diesel engine was to be stopped and not restarted until the maintenance workshop had stripped the engine down and tested the alignment of the long crankshaft! A more realistic comparison in 1950 would have been to compare diesel electrics with the newer 38-class steam locomotive. This was a beautiful machine, very fast, whisper quiet, powerful, and using local coal and water instead of imported diesel oil. No, maintenance costs were not the reason for the steamers' demise. To see why diesel electrics conquered the world, we must look at the biggest and most successful American steam locomotives. Efficiency and running cost Was it the inefficiency and running costs of steam? No, running cost was not the the reason. The Norfolk DECEMBER 1988 79 AMTRAK'S P-30CH DIESEL-ELECTRIC locomotives are built by General Electric for medium and long-haul routes. These powerful 6-axle Co-Co locomotives are rated at 2.24MW (3000hp), have a top speed of 165km/hr and weigh 176 tonnes. and Western Railway resisted the diesel electric demonstrations as late as 1960, showing that their very large modern steam locomotives could equal or outperform any diesel electric units on running costs alone. Those tests were conducted hauling equal train tonnage over the same tracks at equal timetable. The running costs (per tonne hauled) of the huge steam locos were so low simply because those locomotives were so big. One 3-man loco crew could haul any train of the day up any mountain. But competition between railroads being fast and fierce, there was continual striving for yet bigger locos to haul even longer heavier trains. And by the 1930s the design of large steam locos had reached the absolute practical limit. Any increase in steam loco power must mean higher steam 80 SILICON CHIP pressure. This in turn requires larger fire grate area or a larger boiler and cylinders. But the boiler and cylinders could not be increased further in diameter otherwise the locos would not fit through the tunnels. For the same reason, the height could not be increased. The American locos were already up to a metre taller than many Australian machines. Boiler problems No, the only boiler dimension which could be increased was the length. Such an increase could restrict running speed on curves but there is a more critical problem. An overly long boiler has trouble with its fire tubes which run the length of the boiler from the firebox to the smokebox at the front. If the boiler is too long the fire inside those tubes goes cold before reaching the front and boils no more water. So increased boiler length gains nothing. They just could not build larger steam locomotives. Therein lies the reason why diesel electrics won the survival battle. Diesel electrics had the advantage that railroads could couple as many together as they needed to pull a given train and only one loco crew was required. The result? The 175,000 steam locomotives built in the US over the past 120 years are now gone, entirely replaced by 27,000 diesel electrics and a few hundred electric locomotives. And the rest of the world followed suit, largely because they had to. The big three American steam locomotive manufacturers Baldwin, The American Locomotive Company (Alco) and Lima - all had trouble seeing the diesel electric ECONOMY TRANSFORMERS 1-9 ARLEC SUPER TOOL 10 + 2155 240 V6-15V 1A Cat. M12155 $9.95 $8.95 2156 240V 6- 1SV 2A Ca t. M1 2 156 $14.95 $13.95 2840 240V 9V CT Cat. M1 2840 - $5.95 $4.95 2851 240V 12-SV CT 1SOmA Cat. M1285 1 $5.95 $5.50 2860 240V 15V CT 250mA Cat. M1 2860 $5.95 $4.95 6672 240 V 15-30V 1A tapped Cat. M1 6672 $14 .95 $13.95 DB25 CONNECTOR SPECIALS! 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Average conllnuous use 90 minuters • Refills in seconds • ~owered by standard butane gas lighter fuel • Range of easily replaceable screw tips included • Includes metal stand for the soldering iron when workin g • Cap features built-in flint for igniting Portasol tip • Includes snap case for storage Cat. T12639 $89.95 20A, 3 112 digit frequency IO+DISKS IIIO+DISKS 1,IIOO+DISKS $23-95 $22·95 $21 ·95 305 Morphett St, ADELAIDE counter multimeter with capacitance meter and transistor tester. 5¼" 2S/2D DISKS (DOUBLE SIDED) IO+DISKS 100+DISKS 1,IIOO+DISKS Phone : (03 ) 543 7877 SOUTH AUSTRALIA: Electronic Discounters P/L, 7-2VNICAD RACING BATTERY PACK S 15025 Packs of 10 , 2S/20 without boxes, or brand name, just their white paper Jacket and index labels. 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GOLDSTAR 20MHz COMPOSITE MONITOR X145 14 GREEN _, only$89 X14516 AMBER , only $89 10 OR MO RE $85 EACH ina:~fhf ~~ehf8 rJ~~~e~~1fgh~!~~~:! protected Output: standard racing pack lead and terminal to suit S15025 and Tamiya 7·'?.V baneries Char~ Time:Standard charge is 15 minutes for 7·2V baneri es 0-30 minute timer. f111ii'a'1,;;1,1 ALL PRICES PER PACK 10 DISKS DESCR IPTION 1-9 packs 10 + packs 3½" lS/20 3 ½ " 2S/20 3 ½ " 2S/ HO 1 S/20 20/20 2S/40 2S/ HO Red Grn Ylw o,a QUALITY 5mm LEDS VERBATIM DISK SPECIALS! $23 Cat. T12300 FREE STANDING, FOLD UP MAGNIFIER An ecconomicaUy priced ··hands free " magnifier . !ets you take care of all those tricky fine detailed )0 bs so often encountered in electronics. o r any of many other practical uses such as home. work. hobbies etc. Cat. T10020 Normally S14.95 $145 Cat.S15075 $6·75 This unit was developed to allow portable compact disc players to be used in cars by transmitting the headphone output signal directly in to your stereo FM car radio. It will also transmit any mono/stereo signal from any headphone output to any FM receiver. A versatile 12V electric tool tor • Sanding • Engraving • Grinding • Polishing • Cutt ing • Drilli ng • Milling • Erasing . el c Features: Operates on sale . low 12 volts from ma1ns .electnc1ty via AC adaptor (supplied ). li9ht and easy 10 handle with touch switch and lock for continuous running High torque motor. 10.000 A.P M Can drill 2mm holes in steer. 2 year guarantee Contents: • 12V Super Tool • Plugpack AC adaptor • 1 spherical milling cutter • 1 wire brush • 1 grinding wheel • 4 drrtl bits. 0.6. 0.8, 1 0. 1.2mm • Set of 5 chuck collets • 6 eraser sticks • Instruction sheets This spectacular, rugged and compact DMM has a bright yellow high impact plaslic case. It features a frequency counter (to 200kHz). d iode and tran sistor test. continuity (w ith buzzer). capacitance meter. up to 20 amp current measurement and comprehensive AC/DC voltage, current and resistance ranges. CHEC K THESE FEATURES,,,, • Push-button ON/OFF switch • Audible contin uity test • Sing le function, 30 position easy to use rotary switch fo r FUNCT ION and RANGE selection. • Transistor test • Diode test • Quality probes • 1,2 " High contrast LC D. • Full overload protection • 20Amp • Built in tilting bail • Capacitance meter • Instruction manual 091550 ,,,, Normally $165 Special, only $129 Local Orders: (03) 543 7877 Interstate Orders : (008) 33 575 7 All Inquiries : (03) 543 7877 CORRESPONDENCE: P,O , Box 620 , CLAYTON 3168 Telex : AA 151938 Fax: (03) 543 2648 - MAIL ORDER HOnlNE 008335757 (TOLL FREE, STAICTlY ORDERS ONLY) LOCAL ORDERS & INQUIRIES f03J 543 7877 POSTAGE RATES : $1 - $9.99 $10 - $24,99 $25 - $49,99 $50 - $99,99 $100 - $199 $200 - $499 $500 plus The above postage rates are for basic postage only , Road Freight , PANEL METERS GALORE ! We have a great rang e of panel meters at great prices ' Cat.No. Description Price 010500 MU45 0-1mA 12.50 010502 MU45 50-0/50uA 12.50 010504 MU45 0-100uA 12.50 010510 MU45 0-5A 12.50 010518 MU45 0-1A 12.50 010520 MU45 0-1A 12.50 010525 MU45 0•20V 12.50 010530 MU52E 0-1A 14 .50 01 0533 MU 52E 0·5A 14.50 010535 MU45 VU PMetre 14.95 010538 MU65 0-50uA 16 .95 01 0540 MU65 0-1mA 16.95 010550 MU65 0- 100uA 16.95 0 10560 MU65 0-20V 16.95 bulky and fragile items will be charged at different rates . All wholesale and sales tax exempt inquiries to: RITRONICS WHOLESALE, 56 Renver Rd. Clayton_ Ph_ (03) 543 2166 (3 lines) Errors and omissions excepted. Prices and specifications subject to change. :~~!a~SApple ~T;n~i~a~~~~~~s Machines. • is a registered trademark. ' Oenotl:S registered !racfmarks ol their respeclrve owners RELICS OF A BYGONE ERA - SANTA FE's 2900 class steam locomotives used 2-metre high driving wheels to achieve express speeds and pulled a huge tender that carried 32 tonnes of fuel and 120 tonnes of water. Despite their low running costs, nothing could stop the trend to diesel-electric locos and the Santa Fe steam era ended in 1959. trend coming. And they all found that tradition means little in competitive business. Three newcomers to the loco building business had appeared on the American scene. Electromotive Division (EMD) The General Motors Corporation in 1941 established their Electromotive Division which soon became known to the world as EMD, maker today of most diesel electric locomotives (89 % of American production one year). Even when manufacturers outside the USA produce locos, often the diesel engine used is an EMD product. In 1942 EMD unveiled to the world their new philosophy railroads would find it cheaper to purchase EMD diesel electric locomotives ready made "off the showroom floor" and couple as many as needed together for each haulage task. Revolutionary thinking indeed! And it took some years for the railroads to see this new wisdom. Eventually they did. Any number of smaller diesel electric locomotives could be coupled together and controlled in unison by one driver with one motor controller situated at the head end. If a railroad needed 6000hp (4.5MW), simply sell them six 82 SILICON CHIP lO00hp (746kW) locomotives or four 1500hp (1.12MW) units and let the user couple them all together. For loads up to about 25,000 tonnes, the very large couplings and drawbar systems already in use in the USA would allow an incredible number of diesel electric locomotives to be coupled together at the head end. In America six locos coupled .together is a common sight with up to twelve being occasionally used in mountain regions where long cork-screw tunnels inhibit the use of radio controlled locos in midtrain. This "multiple coupled locomotive" philosophy was expounded by the EMD salesmen, pushing the belief that no longer was it necessary to custom-design locomotives for a particular rail-road. General Electric, experienced in electric locomotive production for many years, had less trouble in turning to diesel electric manufacture than did factories like Baldwin. The latter had enormous investments in plant tailored to steamer production, a dedication which severely dented their fortunes. A worse mistake was its failure to see that railroads no longer needed single huge locomotives. Traditionally the big three had custom built large steam locos to the requirements of each railroad. They even designed locomotives specifically for one mountain section of line. Don't laugh, Australian railways did likewise. For example, the NSW 57-class steam locomotive was designed specifically to conquer the Blue Mountain section from Emu Plains to Lithgow. So specific was that design that the 57-class could not run on the northern line of NSW. The wide firebox and ashpan of the 5 7-class would not pass through platforms of stations to the north of Hornsby. So the idea of "general purpose" locomotives took some getting used to. While the big three did eventually enter diesel electric locomotive production, they had to contend with EMD as well as the other two innovative newcomers. For a while the innovations challenged EMD's "stock line" philosophy. But that story we leave till next month. l!tl Subscribers Are you about to change your address? Please advise us by the middle of the month to ensure that your next issue arrives at your new address. Don't miss a single issue j .Electronic t h.ouse number J ? Convert a CB radio IF YOU'RE THE KIND OF READER that can't wait to get the next copy of SILICON CHIP, then why not have the magazine delivered direct to your door? Each month, we'll bring you the best and brightest electronics magazine in the business, put together by Australia's most experienced team. * l for amateur use I' 1 5-element · FM antenna Hili review; Yamaha's brilliant new CD player Constructional Projects for the Enthusiast * Amateur Radio by Garry Cratt * * * The Serviceman's Log Plus - the Original & Best iv Servicoman,. v·inl~g♦ Radio, The Way l Se& It, the Evolut ion of Electric Railwayio; ·· · fOd "bscr·b • e a bi, fill; JtJa;,- 119 JI 0 s111> ,,.,, th. 11t a,.d The Way I See It Sc,-• 1PtioIS 11 Hifi Features & Reviews Collp o,. FREEPOST * SUBSCRIPTION COUPON □ New subscription □ Renewal Start in _ _ _ _ _ __ Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/tow ~ - - - - - - - - - - - Postcode_ _ __ 1 year (12 issues) □ $A42 2 years (24 issues) □ $A84 NZ & PNG (airmail) 0 $A65 □ $A130 Overseas surface mail D $A62 Overseas airmail □ $A120 D $A130 D $A240 Australia Enclosed is my cheque/money order for $ _ _ _ or please debit my □ Bankcard Card No . I □ Visa Card I I I I I I I I I I I I I I I I Signature _ _ _ _ __ _ _ Card expiry date_/_/__ Subscription Hotline We can accept your subscription order by telephone. Just ring us on (02) 982 3935 and quote your Bankcard or Visa Card number and the expiry date. Detach and mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 • No postage stamp required in Australia. W dftJ I L-------------------------------------~ DECEMBER 1988 83 I PRODUCT SHOWCASE I is 40 amps into 20 loads. This has been obtained by using eight Mosfet power transistors in each channel. The all metal cabinet has been designed for installation in standard rack systems and the circuit features comprehensive protection against overloads and excessive temperature. A variable speed fan is fitted for cool and quiet operation. For further information, contact the Australian distributors for Ortofon products, Scan Audio Pty Ltd, PO Box 242, Hawthorn, Victoria 3122. Phone (03) 429 2199. Ortofon's first power amplifier Having recently celebrated 70 years as a manufacturer and 40 years since it made the first moving coil cartridge, Ortofon has just released its first power amplifier, the PPA 600. This unusually styled unit has a rated power of 225 watts per channel into 8 ohm loads and 350 watts per channel into 4 ohm loads. Rated harmonic distortion is less than 0.1 % . According to Ortofon, the PP A 600 is intended for demanding professional and audiophile applications. It can be used in two channel mode or, for higher power output, it can be connected in bridged mode to act as a mono amplifier. In this configuration it can deliver up to 650 watts into 80 loads and 950 watts into 40. Claimed peak current capability New logic probe & logic pulsar The Ultron UT1000 logic probe and UT2000 logic pulser have recently been released by IRH Components at a very good price. The logic probe has a response to 50MHz and will detect pulses with a duration of only 10 nanoseconds. It has pulse latching (memory), a CMOS/TTL switch, and light emitting diodes to indicate under and overvoltage as well as pulse and logic high and low. Recommended selling price is $32 plus 20% sales tax where applicable. The UT2000 logic pulser has an adjustable pulse rate from 0.5Hz to 500Hz and automatic polarity. Maximum output is 84 SILICON CHIP 1000mA with low duty cycles pulses. It can be externally triggered too and has output voltage protection. Recommended selling price is $32 plus 20% sales tax. Both logic probes and pulsers are widely available from dealers or from IRH Components Pty Ltd, 32 Parramatta Road, Lidcombe NSW 2208. Phone (02) 648 5455. Comprehensive screwdriver kit Our article on screws and screwdrivers published last month has already caused a great deal of interest. Just. after we had completed the work on that article Jaycar Electronics released this handy 30 piece screwdriver kit. Essentially the kit is a 215mm long screwdriver with chromevanadium shaft and hex socket to take interchangeable bits. The hardened steel bits are held in place with a magnet inside the hex socket. There are 26 screw bits comprising five standard flat bits, four square drives, six Torx bits (T10, T15, T20, T25, T30 and T40), two Pozidriv (1 and 2 point), four Phillips head (0, 1, 2 and 4 point) and five Hex (Allen) bits. The only one which you're likely to miss is the Tri-Wing which can be picked wpoD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS WOOD FOR CHIPS ... WOOD FOR CHIPS ... WO OD FOR C Check Your Instrument needs in our NEW Price List See Electronics Australia December or call tor a copy 20MHz GOS-522 popular Features low cost scope • Sensitivity : 5mV/div to 5V/div • Bandwidth : de to 20MHz. • Timebase : 20nS/div to 0.5s/div Teat lnatrument. 20MHz GOS-523 with delay and alternate trigger mode Logic Probes & Pul•ro ELP-800 Logic Probe Willuzzer ELP-810 Loge Puser 41.115 41.115 Multimelert • Analogue ST-350 Electricians Tester 33.60 Multimelel'1- Digi!al DIGICOM-121 1 Universal Multimeler 85.00 Features • Sensitivity : 5mV/div to 5V/div • Bandwidth : de to 20MHz • Timebase A : 20ns/div to 0.5s/div (Main) • Timebase B : 20ns/div to 0.5ms/div (Delayed) 40MHz GOS-543 top of the line ~ i5 Q: 0 I.I.. Cl 0 ~ EM'TEK EDM-55 EDM-72B EDM•1105A EDM·1116A EDM-1122 EDM-1135 EDM-1346A EDM-21 16 FLUKE FLUKE-23 FLUKE-73 FLUKE- 75 FLUKE-77 Pen Type DMM 3 1/2 Dg\ROlary Swch 31/2Dgl+ TransTsr 3 1/2 Dgl+Cap.Trans 3 1/2 Dg\9 Faitn 31/2 Dg\7Fcntn 41/2Dg\TrueRMS 31/2 Dgl Booch Mb' AUIO!anging,Sealed Multimeler Multimeter Multimeter 79.35 6S.10 87.85 130.35 147.00 132.05 223.00 301.70 362.25 192.00 ~S.00 • Max sensitivity : 1mV/div Features • Modes : Ch1, Ch2 , Dual, Ch1±Ch2, • Sensitivity : 5mV/div to 5V/div X-Y • Bandwidth : de to 40MHz • Swee : Auto , Normal, Sin le • Timebase A : 20ns/div to 0.5s/div (Main) • Timebase B : 20ns/div to 0.5ms/div (Delayed) a Function Generator GFG-8019 a • Multi-Function with BUILT-IN 10MHz Counter • AM, FM Modulation internal or external • Auto/Manua l Sweep • 0.2Hz to 2MHz Frequency Range • Sine, Triangle, Square, Pulse and Ramp Waveforms • >20Vp-p open Circuit output, 1OVp-p into 50Q • Variable duty cycle and de offset • VCF gives 1000:1 frequency ratio for 0-1 OV input ri -,, )) l: ~ Frequency Counter GFC 801 OF • Frequency Range from 1Hz to 120MHz • Sensitivity <20mV, 10 to 100MHz, <30mV 100MHz to 120MHz 339.00 V ' 200 I JOO ~ • 100 ,<-3. . Frequency Coun1e<1 GFC-801 OF Frequency Count,. GFC-8055F Frequency Counler GFC-8100F Frequency Counter I "" . __, l ~ ~-: GOLDSTAR DM-6135 DM-6235 DM-6335 355.25 572.75 355.25 Function Generalors GFG-2D Fctn Gen .2Hz-2MHz 468.60 GFG-8019 Fen! Gen .2Hz·2MHZ 643.80 GOLDSTAR 3 1/2 Dgl DM-6135+ Mem & Hold DM-6235 + Data Hdd ~ C) Oscinoacopea 20MHz Osciloscope 910.00 GOS-522 88.80 GOS-523 20MHz Scope W/Dly 1210.55 40MHz Osciloscope 1493.30 99.60 GOS-543 118.80 4 (, a C) -,, a ~ CiampMete<t DCP-9 Clamp Meler MCP-4 Clamp Meter POWER SU PPLYT corn Po,ver Supply TA-1 Temperature Prooe 155.00 Panel Melen 88.85 ST-38-lOA-AC 45x45mm AC Pnt Mr 20.00 ST•38· 10V-DC 45x45mm DC Pnl Mr 55.96 ST-38-30V-DC 45,45mm DC Pnl Mr ST-45-lOA·AC 51 x5 1mm AC Pri Mr ST-45 -50/SOuA-DC 51x51mm DC Pnl Mtr Test lnab'umenl Acceasorie• CC6000 GOLDST AR Solt Case 13.80 ST-45-lOV-DC 51x51mm DC Pn! Mr 49.50 ST-45-lOOuA-DC 51x51mm DC Pnl Mr COLINE-TEST-LEAD CAO Probes,Swtctlll 24.65 ST-45-lOV -DC 51,51mm DC Pnl Mr DC-1 Scope Dust Cover 12.40 ST -65-lOA-AC 67x67mm AC Pri Mr . ESCORT-CASE-EC30 Solt Meter Cases 42.55 ·1 ST-65-30A-AC 67,67mm AC Pnl Mr 1 FLUKE-CASE.C25 FLUKE Case 25.30 ST-65-1,00/lOOUAD 67x67mm DC Pnt Mn FLUKE-HOLSTER FLUKE Hlsb' Mdl 70 67x67mm DC Pnl Mb' ! FLUKE-Y8134 FLUKE Test Lead Set 55.20 ST-65-lA -DC 1 ST-65-5A-DC 67x67mm DC Pnl Mtt )) ri 15.30 15.30 15.30 15.55 15.55 15.55 15.55 15.55 19.50 19.50 19.50 1950 19.50 l: ~ ~a C) -,, a )) ri l: 'ti Cl) ~ GEOFF WOOD ELECTRONICS PTY LTD a 229 Burns Bay Road, (Corner Beatrice St.) INC IN Nsw Lane Cove West, N.S.W. P.O. Box 671 , Lane Cove N.S.W. 2066 a Telephone: (02) 4271676, Fax: (02) 428 5198. ri 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $_5.00 to cover postal charges. Next day delivery in Sydney add $5.00. ~ All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED C) -,, )) l: up from specialist tool suppliers. Also included is a 1/4-inch socket adapter and a 1/4-inch socket to hex adapter. The whole kit is housed in a red plastic case. A handy feature of the screwdriver is that you can store a number of bits in the handle. Available from all Jaycar Electronics stores and dealers, the kit is priced at a bargain $19.95. Get in and get one today. Electronic tyre pressure gauge Tyre pressure gauges in service stations are notoriously unreliable and often pocket tyre gauges are not much better; a tolerance of ± 10% is probably the best you can expect. For those that want more precision, this electronic tyre gauge is the answer. Made by Sensym of the USA, it has a liquid crystal display and will measure tyre pressures from 1 to 127 psi with an accuracy of ± 1 psi. When you turn it on, by pushing a red button on the side, it automatically calibrates to zero. It has a microprocessor and operates on three 1.5V button cells (Eveready S13E or Duracell MS13) which are supplied at purchase. After taking a measurement the reading is retained for about 20 seconds and then it turns itself off. We found the unit works well although if you take a measurement with your right hand, the LCD readout is upside down when you take the gauge off the tyre valve to read the pressure. Apart from that small quibble, it is a very good tyre gauge. It sells for $65.20 including sales tax. For further information, contact NSD Australia, Unit 3, 12 Victoria Street, Lidcombe, NSW 2141. Phone (02) 646 5255. "Sensational Price Offer'' Co NTAc T CONTACT CONTACT ELECTRONIC PARTS COMPUTER SPECIALS COMPUTER SPECIALS ■ PLUGS, SOCKETS & SHELLS a: Ill DB 19 DB 23 DB 25 PLUG SOLDER PLUG SOLDER PLUG SOLDER 2.79 2.20 0.70 DISK SlORAGE BOX 100 x 5 1/4" DISK HOLDER FOR'10 ~ 5 1/4' COPYHOLDER DESKlOP ADJ/ ARM 9.00 2.75 23.00 DB 19 DB 23 DB 25 SOCKET SOLDER SOCKET SOLDER SOCKET SOLDER 3.65 2.95 0 .70 IBM AT /XT JOYSTICK ATARI CHALLENGER JOYSTICK 19.00 10.00 DB 19 DB 23 DB 25 BACK SHELL BACK SHELL BACKSEHLL 1.45 1.35 0.60 C-800 WITTY MOUSE MAGIC M WITTY MOUSE 60.00 65.00 XT CASE & LOCK AT CASE & LOCK 60.00 89.95 0 a: 0 _, j I NICAD BATTERIES a: AAA 180 MAH AA 500 MAH C CELL 1.2 AH D CELL 1.2 AH D CELL 4 AH 9 VOLT c RED HOT SPECIALS 150 3.20 2.00 5.80 5.90 11.50 12.00 0_, :I D0342 MOUSE PAD S0225 NUMERIC KEYPAD C0085 ELECTRET MIC INSERT 6.00 2.95 0.45 COMPUTER BITS & PIECES HAND SCANNER HS 2000 MONllOR STAND 12/14' + LOCK KEYBOARD 101 KEY CLICK TYPE SEAGATE HARD DRIVES W/O CONT 375.00 19.00 99.95 ADD ON CARDS CGA SHORT MONOCHROME + PRINTER MULTI 1/0 + FDC PRINTER CARD RS232 SERIAL 1 PORT POWER SUPPLIES 150 W 180 W 220 W lOWER 78.00 75.00 76.00 22.95 49.95 75.00 99.95 139.95 ST ST ST ST ST 225 20M 65MS 238 30M 65MS 251 40M 40MS 251-1 40M 26MS 277R 60M 40MS 350.00 430.00 790.00 1000.00 1000.00 GOLD PLATED HIGH QUALITY LEADS PLUG 10 BNC PLUG 5.95 PLUG 10 RCA PLUG 5.50 PLUG 10 3.55mm PLUG 3.00 BNC BNG RCA RCA PLUG 10 RCA PLUG 3.50 PIONEER SPEAKERS SPEAKER SPEAKER SPEAKER SPEAKER SPEAKER SPEAKER 10' 10· 10· 12· 10· 12· 60W 8 Ohm 100W 8 Ohm 120W 8 Ohm 150W 8 Ohm 200W 8 Ohm 250W 8 Ohm 29.95 54.95 59.96 69.95 79.95 149.95 I,.. 0 " CII !8 I GOLD PLATED HIGH QUALITY LEADS W0201 TV 10 TV GOLD 1.5M W0200 TV 10 VIDEO GOLD 1.5M W0202 VIDEO CABLE SET 3.50 3.50 9.95 Ir 0 "m " CII ALL PRICES INCLUDE SALES TAX JYHOLESALE ENQUIRES WELCOME PRICES VALID WHILST STOCKS LAST CONTACT INTERNATIONAL Suite 2-283 Burbridge Road Brooklyn Park SOUTH AUSTRALIA 5032 PH . 08 ·231 -2202 Fax 08-352-1449 P.O. Box 390, Cowandil/a , South Australia 5033 ················································································································ Mall Order Postage Less than $50 ....... ........................ $3.50 $50 - $99 ······································ $4.50 $100 - $250 ·································· $7.00 Above $250 ................................ $10.00 Heavy Items adds extra • IBM is reg . trade mark of International Business Machines • XT, AT and Atari are registered trade names 0 BANKCARD O MASTERCARD O VISA EXPIRY DATE Card No ...... .......................................... Signature: ......... ... ... .. ................ . .... ..... .... ... .................. .. . . (Note: unsigned credtt card mall ordera cannot be accepted) Name: ........................................................................... . Address: ........................................................................ . . .... •..... ... ..... ... ... ........ .... ... ............ Postcode: .................. . (Please allow 14 DAYS for normal mall and bank clearance delays) Anti-tinkle module from Pre-Pak New car stereo has 4-digit security code Do you have a "tinkle" problem? It is common in domestic installations where there is more than one telephone. Even though the bell circuit is disconnected in one of the phones it may still "tinkle" when the other phone is dialled. This problem can be solved in 4-wire installations by appropriate wiring of both phones but this may not be an option if one of the phones is a two-wire model. Enter the "anti-tinkle" module which is a Telecom approved product. It is wired into the offending phone's bell circuit according to the supplied instructions. Presto, no more tinkle. Priced at $14.95, the anti-tinkle module is available from Pre-Pak Electronics, 27 Cowper Street, Granville, NSW 2142. Phone (02) 569 9797. Large range of rotary switches One of the problems with most car radio tape players is their little teensy knobs and control labelling. Even the dial is often hard to read, especially in bright sunlight. This new model from Philips tackles these problems. Called the DC681, it has a large twocolour liquid crystal digital readout with orange(!) night lighting. Instead of miniature knobs for bass and treble controls, fader and balance, the DC681 has four buttons for these functions. You press the button for the bass setting, for example, and then rotate the large volume control to give the required boost. Two seconds later the volume control rotary switches required in the high performance AC Millivoltmeter described in the August and September issues, Danner Electronics should be able to help. They are located at 51 Georges Crescent, Georges Hall, NSW 2198. Phone (02) 724 6982. reverts to its normal function. All the settings are stored in memory along with the preset FM and AM stations. The memory retains all the stored information even if the car's battery is disconnected. However, if the DC681 is stolen it will not work unless its 4-digit security code is entered in via its pushbuttons. The tape player features music search, Dolby noise reduction and standby mode which allows radio reception while the cassette remains in the deck. This stops entry of dust and rattles which can happen with a partly ejected tape. The unit also switches automatically to radio during fast winding. Power output is quoted as 2 x 20 watts. For further information, see your car stereo dealer. Voracious cable chomper from Arista Electronics store at Engadine No that switch is not being held by a miniature hand - it is a very large rotary 2-pole 6-position switch. It and a large range of more normal rotary switches in sealed, multiwafer and miniature styles are available from Dauner Electronics. If you are looking for the special A new electronics store is now open at Engadine. To be known as Engadine Electronics and Communications and situated at 1/10 Waratah Road, Engadine, the new store will have a wide range of electronic componentry on sale. As well, the new firm will be service agents for Sharp equipment, including marine radios. They will also be selling and installing cellular phones. Their phone number is (02) 520 7495. You had better have plenty of cable around if you buy this voracious cable chomper. It is so comfortable and effective to use you'll find yourself chopping through cables for the heck of it. It goes through 3-core mains cables and shielded cables without turning a (metaphorical) hair. It is availabie from all Arista sales outlets at $59.95. DECEMBER 1988 87 Something to build over the break . . What break, you say! OK - why not take advantage of the couple of days off to build yourself a great kit. Like these superb hi fi speakers, for instance: BONUS! Build yourself a doorbell and we'll throw in an extra 8 Xmas tunes: FREE! Comract Book shel System Put them together in a night or so - and you 'll have a great pair of speakers rated at approx. 40 watts cont (100W max). All you need is some glue, a screwdriver and a bit of time. t~r;i_tive woodgrain type You'll ,need: An enclosure pack 50 (K-4000) Two Woofers (K-3998) Two Tweeters (K-3999) S212 559 50 s13so Normally great value at s249 THIS MONTH ONLY s229 More great kit savings . . . Home Alarm Build your own alarm controller and really save - AND - - - - ,,o...._ only you will know the particular system you ve built. It's easily ......_ good as most commercial alarms, too! Cat K-3424 Normally $149.00 THIS MONTH: s99 Optical Motion Detector Nifty little idea for security alarms, etc. Photosensitive IC senses chang es in light level when someone walks in front of it. Neat - but effective! Cat K-2721 Normally $27 .95 THIS MONTH: 5 1995 Walkabout Wadio Why build yourself an AM radio when you can buy one - possibly even cheaper. Just for the fu n of it! PS - Betcha this beats the pants off one Normally $19.95 you 'd buy! ges cat K-2720 THIS MONTH: S What a great bargain: just in time for the festive season! You can build this superb new musical doorbell, with 16 popular evergreen tunes, and we'll also include FREE a second tune chip with 8 extra Christmas tunes and Carols! What a fantastic project to build -and now you 'll really impress the friends and rels this Christmas! 16 Tune "Standard" Repertoire • Twinkle Twinkle • Eency Weency Spider • Santa Lucia • Are You Sleeping • London Bridge • Butterfly • Coo Coo Waltz (2) • The train is runn ing • Coo Coo Waltz (1) • Lullaby • Clementine • Rocka-a-bye-baby • Little brown jug • Long Long Ago • Mary had a little Lamb • Dream of Home and Mother Cat K-2726 r. Masthead Amplifier Bonus Xmas Tunes! • Jingle Bells• Santa Claus is Coming to Town • Silent Night • Rudolph the Red Nose Reinder • Joy to the World • We wish you a Merry Christmas • O Come all ye Faithful • Hark the Herald Angels Sing This chip normally $10 extra: This month FREEi NORMALLY THIS MONTH Crook TV signal? Build your own masthead amplifier and fix it! Very simple to build, comes complete with all hard ware, power suppl y, etc. Easy one night project. Cat K-5 800 Multi-Purpose Pre-Amp Here's versatility! EA's ingenious new pcb is adaptable to just about any preamp - or the power supply for same. Whatever you want in audio preamps - you 've got! Short form kit - incl udes pcb, op-amp etc; you supply passive components depending on type of preamp you want. Cat K-5010 sggs Proximity/Motion Detector Another new one from AEM. It's an oscillator which reacts to bodies (yours, anyones!) -up to 20 metres away. Adjustable sensiti vity down to 95 centimetres. Think of the applications! Cat K-8100 sa& $49.95 $3995 Remote Switch Transm1 A really worthwhile add-on to for car alarms, etc etc. Suits the devices recently described in Silicon Chip this kit is for the tran smitter only. (EGa spare, one for your partner, etc etc). Cat K-8150 s1sss TELETEXT for your existing TV set! • Not a kit - it's ready built and tested. Just plug it in! • Uses your VCR tuner to save you$$$. • Hundreds of pages of the latest news, sport, finance, weather, information ... all free! • Also receives "subtitles" or closed captions for hearing impaired. • Easy to use! • Designed and manufactured in Australia, with full service back-up through Dick Smith Electronics. • Infra-red remote control INCLUDED at no extra charge! WHY BUY A NEW$1100 TELETEXT TV? ONLY $ 5 79 At last! Now you can receive Teletext - without going to the huge expense of buying a new Teletext TV! Haven't seen Teletext yet? You're missing out on the latest news, stock exchange and financial information, sport results and TAB information, weather reports and forecasts, even recipes, jokes and much, much more. It comes to you absolutely FREE - courtesy of the Australian Television Network. On a normal TV, it's the little colour flashes you see in the black bars between picture frames when your TV "rolls". Unless you have a Teletext TV or decoder, you don't even know they're there! And don't forget, most stations transmit popular programmes with subtitles for the hearing impaired. This Teletext decoder will let you see subtitles too! Until now, you've had to buy a specially equipped TV to receive Teletext. Now you can buy just the Teletext decoder - and keep your TV set! It's not a kit - it's ready to go. And because it plugs into your video cassette recorder, costly duplication of the tuner section is eliminated. So you save! Isn't it time you had the benefit of Teletext in your home? Cat L-4468 ONLY AVAILABLE FROM ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Walkaround throttle makes locos noisy I have built the Walkaround Throttle described in the May and June issues and there is one problem I can't solve. I am running N-scale locomotives with conventional motors; ie, 3 or 5-pole armatures. When used with the above controller the motors emit an audible hum when running and when stationary (under or below motor starting voltage). The hum disappears at zero output from the controller. I have substituted capacitor values as suggested to alter the pulse rate, with the result that the audio tone changes. I have exchanged all on-board chips but this has had no effect. Could this be related to transistor switching noise? Were there any Notes and Errata that I missed? Is a major re-design needed for use with N-scale? I have tried my locos on pure DC and they emit no hum but of course the excellent low-speed starting and running with your design is not possible with pure DC. (R. B., West Richmond, SA). • As we noted on page 38 of the April issue, motor noise can be a problem, particularly at the lower speeds permitted by the controller. It is caused by the transistors rapidly switching on and off the voltage to the loco motor. By varying the duty cycle of the switching (ie, the ratio of the "on" time to the "off" time), the power to the motor is controlled. There is essentially nothing you can do to the circuit to reduce the noise produced by the motors. Your Queries on the Studio 200 preamp I have been reading about your Studio 200 Control Unit and plan to build one but I have some comments and queries. You mentioned that when headphones are in use, the signal connection between the control unit and power amplifier is broken to reduce distortion. However, you seem to have forgotten this at the inputs. There is a line to TAPE OUT via a lkO resistor. Now if the tape player is off, wouldn't this cause distortion in the same way? Perhaps the lkO resistor should be replaced by a buffer stage? Regarding the earth wiring, why not join all input earths together and run one wire back to the OV line on the power supply? Then there is no need for the earth wires on all inputs (except phono) to be connected to the Input/RIAA board. Furthermore, the coaxial interconnections need only to have the screen con90 SILICON CHIP nected at one end only. Also all power lines should run direct between the power supply board. • As noted in the article in the June issue, the main reason for disconnecting the signal to the power amplifier when headphones are in use is to avoid blasting the speakers. Depending on the configuration of the power amplifier's input stages, unenergised transistors can cause distortion. In our experience, the same problem does not occur with tape decks which normally also have a much higher input impedance than power amplifiers. The earthing arrangement in the Studio 200 preamplifier and power amplifier has been devised to minimise common mode signal paths. If you alter the wiring layout, you run the risk that the control unit will be noisy or unstable. unit is working exactly as it is supposed to. However, we wonder if your layout is built on a very thin baseboard. This will tend to amplify any noise produced by the loco motors. We have found that with a "quiet" baseboard, motor noise is not a big problem. As a final thought, you could try reducing the voltage from the power supply. If your power transformer has a 9 or 10-volt tap use that instead of the suggested 12 to 15 volts AC. This will have the effect of reducing the unregulated DC supply to around 14 volts. This will mean a longer duty cycle pulse for a given speed setting and may lead to reduced noise from your loco motors. Query on masthead amplifier Congratulations to all at SILICON CHIP. I have read this magazine since issue one. In the Masthead Amplifier published in the July 1988 issue, is the RF choke 11 a specialised component or is it an easily obtainable item? If not, can a substitute be fabricated and what materials are required? I hope you can help with the answers to these questions. Keep the great stuff coming. (N. W., North Geelong, Vic). • The RF choke in the masthead amplifier is not a critical component. According to Philips data on the OM350, the output RF choke should be 5 microhenries or more. You can make one by winding 27 turns of 0.3mm enamelled copper wire on a short length of 1.6mm diameter ferrite rod. Solution to tape player problem I am writing in response to R. P.'s problem with an indecisive cassette player. Here is an explanation of the cause of the problem. 50V source for Speakerphone testing In your excellent article on the Speakerphone, published in the September issue, you mention a test procedure involving a power supply of between 25 and 50 volts DC. Now that's all very well for these well equipped bods but I don't have such a thing. The closest thing I have to any sort of a power supply is a 12V battery charger. How do I go about getting 50 volts DC without having to spend a mint? (P. B., Emu Plains, NSW). • Hmm. Well, you may not think so, but you do have part of the makings of a 50V power supply. For example, if you connect a lOOOµF capacitor rated at 25VW (VW stands for "volts working" by the way) or more across the output of your battery charger, you will find that you now have a DC power supply which puts out about 24 to 25 volts, with no load connected. That's half way to your 50 volts and you've probably not laid out any money yet if you had the capacitor in your junk box. Fig .1 shows how to connect the capacitor to your battery charger. How do you get the remaining 25 or so volts? Easy. Just connect three 9V batteries in series, as shown in Fig.2. That'll give you between 27 and 30 volts or more, depending on how fresh the batteries are. Now connect those three batteries in series with the battery In auto reverse cassette players one of the reels has a tape movement sensor which generates pulses while ever the tape is moving. When the player comes to the end of the tape, the pulses cease and an electronic circuit operates the direction changing solenoid. The player then automatically begins to play the other side of the tape. This circuit is essentially a Fig.1: by connecting a lO00µF capacitor across a typical 12V battery charger you can get about 24-25V DC. 9V 9V 9V Fig.2: three fresh 9V batteries in series will give you 27-30V DC off load. This can be connected in series with the output of Fig.1 to give over 50V. charger supply and you'll have a total supply voltage of just over 50 volts. To achieve this, connect the negative output from the battery charger supply to the positive output of your composite 2 7V battery. The resulting "stacked" supply will be your desired 50 volts or close to it. Such a supply will only be capable of delivering about 10 to 15 milliamps but that will be quite adequate for testing the Speakerphone, as outlined in our September article. On the other hand, your battery charger-cum-DC power sup- "missing pulse detector" similar to the "End of File Indicator" featured in the February 1988 issue of this magazine. The sensor can be in the form of two spring fingers rubbing against a segmented disc, mounted under one of the hubs, or a reed relay used with a circular magnet under one of the hubs. Some small personal cassette players use an optical system with ply should be capable of delivering one amp or more before the output voltage drops too much. This can be quite handy as a substitute for a proper power supply. Oh, and you don't really need a battery charger at all, to get 50V DC. Just connect 5 9V batteries in series. That will give you close to 50V straight away. That'll set you back about $8 or so, including the battery snap connectors. And remember, you don't need 50 volts anyway. Anything over about 25 volts will do. an infrared LED being shone on an optically segmented disc, with a phototransistor creating the pulses. I would suggest that R. P. check to see if any pulses are coming from this sensor and if they are being acted upon correctly by the rest of the circuit. I have seen one cassette player that was acting in the same manner as R. P.'s. It used plastic gears to transfer motion from the motor to DECEMBER 1988 91 Silicon Chip Back Issues Issue Highlights November 1987: Car Stereo in Your Home; 1GHz Frequency Meter; Capacitance Adapter for DMMs. December 1987: 100W Power Amplifier Module; Passive lnfrared Sensor for Burglar Alarms; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter. January 1988: ~ 1:1m1....tjowtie UHF ~• ower Supp,_ ,.,.,-nc.-rrnger; Subcarrier Adapter M Tuners. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems; Simple Door Minder. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Low Cost Function Generator; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger ; Headphone Amplifier for CD Players. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; Automatic Light Controller; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show. August 1988: Plasma Display; Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; Switchmode Charger for 12V Gel Batteries; Vader Voice. October 1988: Stereo FM Transmitter; High Performance FM Antenna; Led-Light House Number; Matchbox Crystal Set. November 1988: Amplifier Module; Plasma Display; Car How to Quieten the Computer 120W PA Poor Man 's Safety Light; Fan in Your BACK ISSUES ORDER FORM Please send me a back issue for: D November 1987 D December 1987 D February 1 988 D March 1988 D August 1 988 D May 1988 D June 1988 D July 1988 D April 1988 D Sept.1988 □ October 1 988 □ November 1988 Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my D Bankcard Card No --L---"----'----'----'-----'---'----'-----'- - - - ' - ' - -' - -' - -- ' - -..,___, . I _ Signature _ _ _ _ _ _ _ _ _ Card expiry date_/_/_ _ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/tow .__ _ _ _ _ _ _ _ _ _ _ _ Postcode____ D Visa Card Price: $A5.00 each (includes postage). Overseas orders add $A 1.00 per issue for postage. NZ & PNG orders are sent by air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 ~-------------------------------------J 92 SILICON CHIP Protection for 60W loudspeaker I am writing concerning the Studio 200 power amplifier described in the February issue of SILICON CHIP. I have built this unit and find it to be a great amp. I have it connected to two sets of loudspeakers, one pair rated at 150 watts each and one pair rated at 60 watts each. I was wondering if you could suggest a circuit to protect the less powerful speakers, in case I accidentally raise the volume too high. I realise that since the amplifier is rated at 100 watts per channel I should not be able to blow the loudspeakers. However, I would like to be certain that I do not cause damage to them. Also, if I wished to have the two speaker systems as local and remote, would I just be able to connect the output of the amp modules to a 2-pole 3-position rotary switch, so as to select bet- the hubs. A piece of dirt had become stuck in the teeth of one gear so that it could not turn completely. As the gear turned it would jam and stop the tape. This then caused the motor to change direction whereupon the gear would jam again. Removing the obstruction fixed the cassette player. (M. A., Gore Hill, NSW). • Thanks, M. A. We have also been told that intermittently jamming cassettes are often the cause of problems with auto reverse tape players, particularly those in cars. Tapping the cassette housing will often clear the problem for the time being but the fault may strike again some time later. Sensitivity adjustment on 1GHz DFM I am having trouble adjusting the sensitivity of my 1GHz Frequency Counter (as described in the November 1987 to January 1988 issues). At switch-on, the LED illuminates but will not change state no matter what adjustments are ween local, remote or both? Last but not least, I would like to congratulate you on the great work you have put in to the magazine. I have been reading it since the second issue and I love it. Keep up the good work. (T. I., Matraville, NSW). • Your cautious approach to speaker protection is a good one. You have to bear in mind that the 100W modules in the Studio 200 can probably deliver 200 watts or more when driven into clipping, before their associated PTC thermistor acts to limit the current. The solution is quite simple though. All you have to do is to connect a PTC (positive temperature coefficient) thermistor of appropriate rating in series with the speakers you wish to protect. As it happens, the thermistor specified for the 50 watt amplifier module described in our December 1987 issue will be made to VRl. Even tapping VRl causes little disturbance to the LED. Also, the parts list and circuit diagram both .call for 15 0.0lµF miniature ceramic capacitors but the parts overlay only shows 14. What happened to the fifteenth? I am hoping you can help me with this problem. (G. W., Willmot, NSW). • As a first step in solving this problem we suggest you check the main counter board very carefully for any board defects such as solder bridges between tracks or open-circuits in tracks. On this closely packed board with its fine tracks it is quite easy to miss a defect. You need strong light and, ideally, a magnifying glass. Once you are sure that there are no board defects, you can go on to check the logic states of the 10116 triple line receiver; ie, the device which drives the LED in question. Since the 10116 is an ECL (emitter coupled logic) device, its logic states are quite different to those for the more common CMOS logic devices. Instead of logic 1 being just the ticket. It is a Raychem type RDE 115 Polyswitch. It is a stock item from Jaycar Electronics (Cat. No. RN-3415) at $8.95 each. You will need one for each 60 watt speaker box. We suggest you install each Polyswitch inside the speaker box. As far as a speaker selector switch is concerned, your suggestion is workable although the readily available rotary switches from electronic parts retailers do not really have rugged enough contacts to carry the relatively high currents involved. As a partial solution, we suggest that you use a 4-pole 3-position switch, and parallel the switch sections so that you get a higher current capability. A better solution may be to use a pair of mains-rated DPDT switches with 10-amp contacts. You need one switch for each pair of speakers. To select both speaker systems, both switches should be on. close to + 5V and logic 0 being close to 0V, the ECL logic 1 corresponds to - 0.9V below the + 5V supply while ECL logic 0 is -1.75V below + 5V. This means that the pins on an ECL device should be higher than + 4.1 V or lower than + 3.25V, assuming that the 5V supply is exactly 5V. So go through and check each of the pins on the 10116. Pins 9 and 10 should be close to + 3. 7V, pins 1 and 16 should be at + 5V and pin 8 should be at 0V. All the other pins should be at ECL logic levels. Note also that since the 10116 is a differential device (with differential inputs and outputs), its inputs and outputs are complementary. For example, if output pin 6 is high, its complementary output at pin 7 will be low. Similarly, if output pin 3 is high, pin 2 will be low. By checking the voltages right around the device you should be able to isolate the problem. · As far as the 15 .0lµF capacitors are concerned, the component layout diagram is correct. There are only 14. DECEMBER1988 93 Index to Volume 1: Nov. 1987 - Dec. 1988 Features Electric Railways 11 /87 76 Your House Wiring Could Kill You 12/87 6 Using Your VCR to Tune UHF TV Stations 12/87 40 Amateurs Link Coast to Coast 12/87 50 AT-Compatible Kit Computer 01 /88 12 The 1987 CESA Hifi Awards 01 /88 68 OTC's Automatic Seaphone Service 02/88 6 Electronics and the Big Cat 02/88 1 4 Easy Tips on Headphone Repair 02/88 50 South Pacific: The Electronic Version 03/88 6 New Life for Radio Cassette Players 03/88 12 Vintage Radio: How It Began , Pt.1 04/88 6 Vintage Rad io: How it Began, Pt.2 07/88 4 Amplifier Headroom: It It a Con? 09/88 8 Sony's Mind Blowing 8mm Video Gear 10/88 4 Electronics & Brock's BMW Blaster 11 /88 4 All About Screws & Screwdrivers 11 /88 8 Quieten the Fan in Your Computer 11 /88 76 The Technology Letters, Pt.1 12/88 4 Electronics & Holden's V6 Engine 12/88 42 Kit Clinic 11 /87 Design & Theory 03/88 65 High, Low Sink & Source Explained 04/88 10 What is Negative Feedback? Pt.1 05/88 42 Motorola's MC3334P Ignition IC 06/88 1 O What is Negative Feedback? Pt.2 07/88 50 National Semiconductor's LM833 Op Amp 07/88 70 What is Negative Feedback? Pt.3 08/88 54 A Look At Insulated Tab Triacs 09/88 58 Motorola's MC34018 Speakerphone IC 09/88 82 What is Negative Feedback? Pt.4 Digital Fundamentals 11 /87 12/87 01 /88 02/88 83 90 86 85 03/88 81 04/88 81 05/88 84 06/88 86 08/88 63 09/88 66 94 Lesson 1 : Binary Data Lesson 2: Digital Logic Elements Lesson 3 : Digital Circuits Lesson 4: Understanding & Using Flipflops Lesson 5: Counters & Shift Registers Lesson 6: Combinational Logic Circuits Lesson 7 : Memory Circuits Lesson 8: Introduction to Microcomputers Lesson 9 : Input & Output Operations Lesson 10: Programming Microcomputers SILICON CHIP 12/87 01 /88 02/88 03/88 04/88 05/88 06/88 07/88 08/88 09/88 10/88 11 /88 12/88 6 The Birth of Steam & Electric Locos 68 Steam Locomotives Come of Age 4 The Problem of Braking 80 Australia's First 100 Years 76 Electrics in Australia 74 The Sydney & Blue Mountains Systems 76 The First Electric Mainline System 80 The First 3-Phase AC Electric Railway 84 15kV 16.6Hz AC In Northern Europe 76 Electrification in Central Europe 88 The Queensland 25kV Suburban System 76 Queensland's Powerful New Electric Locos 96 A Look At Diesel-Electric Locomotives 76 Why Diesel-Electrics Killed Off Steam Vintage Radio 05/88 06/88 07/88 08/88 09/88 10/88 11 /88 12/88 6 Collecting Vintage Radio Receivers 16 Cleaning Up the Chassis 10 Checking & Repairing the Valves 4 Capacitors Cause Lots of Problems 4 Checking & Replacing Resistors 8 Checking Out the Power Supply 34 What To Do About the Loudspeaker 14 Restoring the Dial Mechanism The Way I See It 1 1/87 14 They'll Sell you Anything But Don't Ask Them to Fix It 12/87 87 Is the Electronic Servicing Industry Dragging Its Feet? 01 /88 82 Information Has Its Place But What About Knowledge 02/88 70 Worth Preserving : A Colourful Slice of Electronic History 03/88 72 The Quest for Ultimate Hifi is Half the Fun 04/88 16 Audio Power Ratings - Right Back Where We Started From 05/88 12 Is UHF TV as Good as It's Cracked Up To Be? 06/88 6 For All Practical Purposes, Mr Fixit Has Had His Day 07/88 18 Are Computers Turning Us Into Automatons? 08/88 14 Some Things Are Enough to Make a Grown Man Cry 09/88 22 Could We End Up Drinking Nickel Cadmium Cocktails? 10/88 36 Fly By Wire: Is It Safe From Electromagnetic Interference? 11 /88 28 Look Out TV Servicemen: VCRs Are Now Disposable 12/88 44 UHF TV Problems in the lllawarra Region Serviceman's Log 11 /87 12/87 01 /88 02/88 03/88 04/88 46 73 56 60 50 54 05/88 56 06/88 38 07/88 08/88 09/88 10/88 34 28 38 44 11 /88 54 12/88 62 With Friend's Like That All This In A Brand New Set When The Chips Are Down His Master's Voice A Baffling Exercise Beating An Intermittent When the Heat's On Double Or Quits - Toss Ya Ring Out The New, Ring In The Old Sounding Out a Video Recorder Sound Reasons For Confusion Helping The Old Folk At Home Curing Woolly Pictures At Wollongong My Friend (The Enemy) Flicker The Customer Has No Idea TETIA TV Tips 12/87 66 Rank Arena C2239 (82 Chassis) 01 /87 59 Blaupunkt (Bridge Rectifier Chassis) 02/88 64 Sony KV1 800-AS 03/88 54 Thorn 9904 (Q Chassis) 04/88 55 Sony KV1 800-AS 05/88 60 Philips K9 Chassis 06/88 42 Rank Arena C2205 07/88 36 HMV 12613 (Braddon) 08/88 31 Philips (CA826) (Toshiba Chassis) 09/88 44 General Electric TC53L2 10/88 49 National TC1401 A 11 /88 60 Sony KV1830AS (Early Version) 12/88 67 Kriesler 59-4/5/6 Telecommander Remote Control 12/88 67 AWA Thorn 3500 Series Hifi Reviews 11 /87 11 Marantz PM-35 Integrated Amplifier 12/87 17 Realistic Nova-1 5 Loudspeakers 01 /88 32 Marantz CD-94 Compact Disc Player 02/88 30 Sony RA-N77ES Stereo Power Amplifier & TA-E77ES Stereo Control Amplifier 03/88 16 Tandy CD-1 500 CD Player 04/88 15 Arista CDS606 Compact Loudspeaker System 06/88 15 Realistic Optimus 304 Loudspeaker System 07/88 .16 Amcron MA-1 200 Power Amplifier 10/88 20 Yamaha CDX-1110 CD Player 12/88 18 Harman Kardon PM665Vxi Stereo Amplifier Circuit Notebook 11 /87 62 DC Speed Control For Model Motors 11 /87 62 Measuring the Tracking of Dual Potentiometers Projects 11 /87 20 Capacitance Adaptor for DMMs 11/87 32 1GHz Digital Frequency Meter, Pt.1 11/87 54 Car Stereo for Your Home 11/87 66 Off Hook Indicator for Telephones 11/87 72 Portable Electronics Workbench 12/87 10 100 Watt Amplifier Module 12/87 28 24V to 12V Converter for Trucks 12/87 33 Passive lnfrared Movement Detector 12/87 46 Speedi-Watt Lamp Dimmer 12/87 76 1GHz Digital Frequency Meter, Pt.2 01/88 14 High-Performance UHF Antenna 01/88 24 Electronic Chime for Telephones 01/88 38 Dual Tracking ± 18.5V Power Supply 01/88 48 1GHz Digital Frequency Meter, Pt.3 01/88 64 Subcarrier Adaptor for FM Tuners 01/88 71 The Flexo Shortwave Antenna 02/88 18 Protector Car Burglar Alarm 02/88 36 Studio 200 Stereo Power Amplifier 02/88 46 End-of-File Indicator for Modems 02/88 53 Build the Door Minder 02/88 56 Low Ohms Adaptor for Multimeters 11 /87 63 How to Obtain -5V From A +5V Supply 11 /87 63 Frequency Comparator With Visual Display 12/87 18 Low Power RAM EPROM Emulator 12/87 18 Simple Transistor Oscillator 12/87 19 Courtesy Light Delay Switch 12/87 19 Voltage Regulator For 1 2V Alternators 01 / 88 22 Sequential Lamp Flasher For Cars 01 /88 22 High Impedance Op Amp With Input Protection 01 /88 23 Crowbar Over-Voltage Protection For Power Supplies 01 /88 23 Substituting Electrolytic Capacitors 02/88 34 Thermatic Fan Timer For Cars 02/88 34 Dynamic Noise Reduction For Cassette Players 02/88 35 El Cheapo Car Burglar Alarm 03/88 38 Adjustable Load For Power Supplies 03/88 38 Synchroscope For Frequency Comparison 03/88 39 CAO Probe Modification 03/88 39 Precision Reset For Microprocessors 04/88 50 High Speed Pulse Amplifier 04/88 50 Headphone Noise Monitor For Power Amplifiers 04/88 51 Quiz Game Using a CMOS Latch 04/88 51 VU Meter For Tape Dubbing 05/88 50 Voltage & Current Metering For Power Supplies 05/88 51 Improvements For Modem Endof-File Indicator 03/88 18 Line Grabber for Telephones 03/88 26 Remote Switch for Car Burglar Alarms 03/88 40 Endless Loop Tape Player 03/88 43 Technilab 301 Function Generator 03/88 56 Old-Time Crystal Radio 03/88 60 Build Your Own Light Box 04/88 28 Headphone Amplifier for CD Players 04/88 32 Walkaround Throttle for Model Railroads, Pt. 1 04/88 47 Build a Slave Flash Trigger 04/88 60 A pH Meter for Swimming Pools 05/88 18 Optical Tachometer for Aeromodellers 05/88 32 High Energy Ignition for Cars 05/88 44 Walkaround Throttle for Model Railroads, Pt.2 05/88 62 Ultrasonic Car Burglar Alarm 05/88 72 Build the Party Light 06/88 28 Studio 200 Stereo Control Unit, Pt.1 06/88 44 Convert Your Car to Breakerless Ignition 06/88 56 Automatic Light Controller 06/88 62 Mega-Fast Nicad .Battery Charger 07/88 14 Fuel Cut-Off Solenoid for Cars 07/88 30 Booster for TV & FM Signals 07/88 40 Studio 200 Stereo Control Unit, Pt.2 07/88 56 The Discolight Light Show, Pt.1 07/88 74 Tone Burst Source for Amplifier Testing 08/88 8 Build a Plasma Display 08/88 18 High Performance AC Millivoltmeter, Pt.1 08/88 38 Universal Power Supply Board 08/88 42 The Discolight Light Show, Pt.2 08/88 56 Remote Controlled Chimes Unit 09/88 14 Hands-Free Speakerphone 09/88 30 Electronic Fish Bite Detector 09/88 46 High Performance AC Millivoltmeter, Pt.2 09/88 60 the Incredible Vader Voice 10/88 14 FM Stereo Transmitter 10/88 28 High Performance FM Antenna 10/88 52 The Classic Matchbox Crystal Set 10/88 64 The Led-Light House Number 11/88 14 High Power PA Amplifier Module 11/88 40 Poor Man's Plasma Display 11/88 64 Build a Car Safety Light 11/88 68 Add a Headset to the Speakerphone 11/88 87 Dynamic Balancing for Electric Fans 12/88 26 1 20 Watt Public Address Amplifier 12/88 34 Car Antenna/Demister Adaptor 12/88 50 Diesel Sound Simulator for Model Railroads 05/88 51 High-Q Notch Filter 06/88 69 Dual Power Circuit With Back-Up Battery Indicator 06/88 69 Brighter Flashing Lamp For Alarms 06/88 69 Flashing Pilot Lamp 07/88 14 Fuel Cut-Off Solenoid For Cars 08/88 34 Telephone Ring Simulator 08/88 34 DC Stereo Volume Control 08/88 35 Digital Lissajous Frequency Comparator 09/88 34 National Semiconductor's LM12 150W Op Amp 10/88 70 Off Peak Indicator For Hot Water Systems 10/88 70 Audio Overload Detector 10/88 71 Long Interval Timer 11 /88 32 Knightrider LED Scanner 11 /88 32 12-240V 60VA Inverter 12/88 59 Charger for 1 2V Gel Batteries 12/88 59 Constant Current Nicad Charger 04/88 67 Mobile Antenna For The VHF & UHF Bands 05/88 70 Designing & Building Attenuators 06/88 72 Build An RF Sniffer Probe & Preamplifier 07/88 64 A Look At Amplitude Companded Sideband 08/88 84 How To Get The Most Out Of Nicad Batteries 09/88 84 Switchmode Charger For Gel Batteries 10/88 84 Convert a CB Radio to the 28MHz Amateur Band 11 /88 92 What's All This Talk About SINAD? 12/88 70 SSS Adaptor For Shortwave Receivers Safety Watch 03/88 03/88 03/88 10/88 71 71 71 71 VCRs & Water Don't Mix Hazardous Power Cords Safety With The Iron Electric Shavers Should Be Checked Amateur Radio Introducing Amateur Radio Tuning In To The VHF Bands Getting Started on Amateur TV Line Isolation Unit for Phone Patch Operation 03/88 68 Antennas For The VHF & UHF Bands 11 /87 12/87 01 /88 02 /88 90 73 76 74 Notes & Errata 01 /88 03/88 03/88 06/88 06/88 95 96 96 95 95 07/88 95 08/88 95 08/88 95 08/88 95 08/88 95 09/88 103 10/88 99 10/88 99 11 /88 104 11 /88 104 11 /88 104 12/88 96 Digital Fundamentals Capacitance Adaptor for DMMs 24V to 12V Converter Remote Switch for Car Alarms Passive lnfrared Movement Detector Remote Switch for Car Alarms 24V to 12V Converter Protector Car Burglar Alarm Optical Tachometer Studio 200 Stereo Control Unit UHF Remote Chime/Doorbell Studio 200 Stereo Control Unit Remote Switch & Remote Chime Low Ohms Tester for DMMs Switchmode Battery Charger Hands-Free Speakerphone Stereo FM Transmitter DECEMBER 1988 95 CEN Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) 16 ($7.40) 17 ($7.80) 18 ($8.20) 19 ($8.60) 20 ($9.00) 21 ($9.40) 22 ($9.80) 23 ($10.20) 24 ($10.60) 25 ($11 00) 26 ($11 .40) 27 ($11.80) 28 ($12.20) 29 ($12.60) 30 ($13.00) Name ... Address ... Suburb/Town Postcode . Enclosed is my cneque or money order for $ ....... . .... . .... .. . ... . D Bankcard D Visa Card Card No . or please debit my !~~~-~~~~-~~~~~-~~~~~ Signature ........ . FOR SALE NEW 64K-256K PRINTER BUFFER design release . VER 4.0 and REV G boards now available. Double-sided PCB, EPROM and instructions: $39 .00 . Optional additions include 2 x THE BUBBLE-ETCHER Our Bubble-Etcher now has a heater. Reheat the etchant when you need it. Let the air bubbles do the stirring. The perspex tank forms a vertical slot. You see the etching proceed. Suits boards up to 1 2 x 1 0-inch. Ask us for a pamphlet. Sesame Electronics Pty Ltd, PO Box 452, Prahan 3181. Phone (03) 527 8807. 96 SILICON CHIP Advertising Index Allied Capacitors ...... ...... .... .. 21 Altronics ..... ..... ........ .... .. 38-41 Arista Electronics .............. ... 66 Avtek ... .... ..... ....... .... ... ...... IBC Ballarat Electronic Supplies .. . 1 5 Bell lRH ... .... .. .. ............ ... ...... 9 Contact International .. ... .. ..... 86 David Reid Electronics ... ..... .. 33 Dick Smith Electronics ..... 12, 13 48,49,88,89 Electronic Solutions ...... .. 60,61 Geoff Wood Electronics .. ...... 85 Goldstar ..... .... ..... .. .. ... . : ..... IFC Hycal Instruments ................ 1 5 Jaycar Electronics ... ....... 22-25 72-75 J.V. Tuners ............... .. ... ..... 67 Kenwood Australia .. ... .... ... OBC Pre Pak Electronics ... ........ ... 69 RCS Radio .......... .... .. ... .. ... .. 4 7 Rod Irving Electronics ......... .. 81 Scan Audio .. .. ............ .. ....... 21 Sesame Electronics ....... ...... 96 7 -segment LED front panel display of percentage full, 1 to 99 copies select, 3 polled computer inputs, printer switches, computer switches, and serial converter boards. For a free catalog send a 37c stamp to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . RADIO/TV RESTORERS - We have a large stock of new valves . Send SAE for list or phone Shellharbour TV Service, 26B Mary St, Shellharbour, 2529. (042) 95 1175. BOOKS & PLANS LOW SPEED GENERATORS for windmills, water turbines, steam engines. The definitive book: " The Homebuilt Dynamo" (1987), 182 pages, 8.5" x 1 2", hardback. Generator design and construction with ceramic magnets. PC Boards Printed circuit boards for SILICONCHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd , Bexley, NSW 2207. Phone (02) 587 3491. • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555. • Marday Services, 2139 Great North Rd, Avondale , Auckland, NZ. Phone 88 5730 . Complete plans, 268 photographs, step-by-step construction details. $A85.00 postpaid airmail (brochure $A5 .00 refundable). Todd-Forbes Publishing, 627 West Coast Road, Oratia, Auckland . Notes & Errata FM Stereo Transmitter, October 1988: the O.OlµF filter capacitor connected to pin 12 of the IC should be 0.00lµF. With the O.OlµF in place the transmitter will not work in stereo. NOW SAVE EVEN MORE ON THESE OUTSTANDING MODEMS Avtek, the longest established Australian modem manufacturer, now gives you a chance to get even better value when you buy. Just check the features and the prices of Avtek and you'll see why it's the modem chosen by more and more PC users. More compact and reliable than most and suitable for data transfer between PCs, on-line services, E-mail and all videotex facilities like VIATEL (Model 123 only). Available as a standalone RS232 model or as a plug-in true ½ card for IBM PCs and compatibles. Specifications: Data Standards CCITTV.21 (300/300 baud full duplex). Data rates - CCITTV.23 (1200/75 baud). AN/DEAL FIRST MODEM! A fuly automatic operation, HAYES-compatible smart modem. Choose from 3 models (internal or external) model 21/23 300/300, 1200/75 12 300/300, 1200/1200 123 300/300, 1200/1200, 1200/75 $ 325 325 399 ,~ID:llLlffill\l\\\. 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