Fullscreen HTML5Med Res (??MB)HTML4

MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP Announcing Pioneer Hill Software FOR SALE SpectraPLUS 24bit DAQ ADC spectrogram, t.h.d. and i.m.d. analysis, f.f.t, acoustic tools, 3D surface plot, sig. gen. etc. Fully shielded SpecctraDAQ200 ADC/DAC 24bit/192kHz dual channel, Wolfson. AKM converters … USB3 interface to laptop/PC As 2ch. 24bit recorder t.h.d. = 0.002%max see : www.spectraplus.com Order direct, USA contact : John Pattee (pioneer<at>spectraplus.com) Local agent : DSCAPE Melbourne s/w , h/w package ca. USD $1500 Aus. Distributor : Julian Driscoll CEO jcdrisc<at>tpg.com.au for support TEKTRONIX 316 10MHz valve oscilloscope. Excellent condition. In use until 1989, then storage, Sydney. Suit collector/restorer. No probes. Best offer above $140.00. email kim.hague-smith<at>tpg. com.au tronixlabs.com - Australia’s best value for hobbyist and enthusiast electronics from adafruit, DFRobot, Freetronics, Raspberry Pi, Seeedstudio and more, with same-day shipping. CRO & BITS for robotics. BWD 1722 Oscilloscope plus manuals. Assorted motors, cogs, solenoids, magnetic clutches etc removed from photocopier. Free if able to pick up. NE Victoria. tevitarobson<at>gmail.com for details. PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au PCBs & Micros: SILICON CHIP can sup- ply PCBs and programmed microcontrollers and other specialist parts for recent projects and some not so recent projects: www.siliconchip.com.au or phone (02) 9939 3295. LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au KIT ASSEMBLY & REPAIR VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $10 inspection fee plus charges for parts and labour as re- quired. Labour fees $35 p/h. Pensioner discounts available on application. Contact Alan on 0425 122 415 or email bigal radioshack<at>gmail.com KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com DAVE THOMPSON (the Serviceman from SILICON CHIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Phone NZ (+64 3) 366 6588 or email dave<at> davethompson.co.nz ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words plus 95 cents for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. Ask SILICON CHIP . . . continued from page 94 Dog silencer overheats I built the Dog Silencer (SILICON CHIP, July 1999) from an Oatley Electronics kit but I’m having trouble with siliconchip.com.au it. The MTP3055 Mosfets on the output amplifier have 1W 10Ω resistors on their drains which keep overheating and I can’t see why. I replaced the Mosfets and disconnected the output transformers so there is no load and still the resistors cook. The output transformers get hot too. It’s a simple circuit and shouldn’t be a problem so any help you can give us would be appreciated as the dogs just keep on barking. (T. D., Perth, WA). • Try connecting a 1N5819 Schottky diode across each transformer primary with the cathode to 12V and the anode to the junction of the 10Ω resistor and the transformer winding. The diode will clamp the back-EMF rather than the 10Ω resistor via the Mosfet. Also, the frequency could be adjusted for March 2016  95