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By JOHN CLARKE Watch two TV channels at once! If you want to watch two TV channels at once, this Pic­ture-in-Picture unit will come in handy. It will enable you to check on the golf, cricket or your second favourite show while also watching another channel. It’s easy to build and all func­tions are infrared remote controlled. TV Picture-in10  Silicon Chip H OW MANY times have you wanted to see what is happen­ing on a second TV channel while watching another program? It may be that the program that you want to watch next starts before the present one is finished or there are two programs that you want to see but they are showing at the same time. You may also want to watch another channel while the advertisements are on but not want to miss the show when it comes back on. With this Picture-in-Picture unit you can do all those things and more. Picture-in-picture or PIP on a tele­ vision screen means that there is a second small picture of another channel superimposed on the main picture. It is usually about 1/6th the size of the screen and so it does not normally detract too seriously from the main program. If it does cause problems, it can either quickly be switched off or “flicked” (using the ROTATE button) to another corner of the screen. You can also quickly swap the PIP with the main picture, just by pressing the SWAP button on the remote control. When this is done, the original PIP is viewed full size, while the original full-sized program is shrunk to the smaller PIP area. The sound is automatically swapped with the picture. Note that you can also swap the sound from one channel to the other, so that either the main or PIP channel can be heard. Another very useful feature is a sound muting facility. This is particularly handy for advertisements which are usually at a louder volume than normal program material. As shown in the photos, the TV Picture-In-Picture Unit is housed in a slimline plastic case with terminals at the rear for the audio and video connections. On the front is the power switch, a power indicator LED and a window for the infrared remote control sensor. The handheld remote control takes care of all functions, except for power on/off switching. To make the construction easy, the PIP unit is based on a pre-built module which performs all the video functions. We have added in the audio and remote control facilities to complete the unit. What you need Two video sources are required for the PIP unit to operate and this would normally be provided by two video players. Just about every household has at least one VCR and many have two, although often the tape transport mechanism in the older unit has failed. Main Features • • • • • • • • • Adds a small picture (PIP) of another channel to one corner of the TV screen PIP can be displayed in any corner of the screen Main picture & PIP can be swapped at the press of a button Audio automatically swaps with picture swap Audio signal can be either for the main picture or for the PIP Audio mute facility Stereo or mono audio Remote control functions for all features Direct video or RF modulator output (channel 0 or 1) This handpiece remotely selects all the functions of the Picture-In-Picture Unit. It lets you move the PIP to any corner of the screen, swap between the PIP and the main picture, and swap and mute the audio. -Picture Unit April 1997  11 Don’t do this unless you are experienced with TV/video circuits and know exactly what you are doing. Be aware also that some older TV sets may have a live chassis and that any modifica­tions will invalidate the set’s warranty. Add in any technical difficulties that you may encounter (signal levels, etc) and you can see why we recommend the two-VCR approach. Fig.1 shows a typical installation for the PIP Unit. The two VCRs receive the incoming RF from the antenna via a splitter and their audio and video outputs are fed to the PIP Unit. The RF modulated output from the PIP unit (channel 0 or 1) is then fed to the antenna input (RF IN) of the TV receiver. Alternatively, the audio and video outputs from the PIP Unit can be fed to the TV receiver, provided the set has provision for these inputs. The left and right (L & R) audio outputs can also be fed to a stereo amplifier. Note that although Fig.1 depicts stereo VCRs, mono VCRs can also be used – just use mono cables and connect to either the left or right audio channel of the PIP unit. Block diagram By default, the PIP appears in the bottom righthand corner of the screen when it is turned on. It can be moved to any of the other corners of the screen at the press of a button. Note that the PIP quality is not as good as the main picture. That doesn’t matter – it’s the tuner section of the older unit that we’re really after and provided that still works, it can be pressed into service. If you don’t have a second VCR, you can probably obtain a junked unit quite cheaply from a video repair shop. Don’t worry too much about the tape transport mechanism – just make sure that the tuner/RF section works. An old Beta player could probably be picked up for a few dollars (or even 12  Silicon Chip given away), for example. Although using two VCRs to provide the two channels is the obvious way to go, it may be possible to modify the TV set in some cases so that it can function as a signal source. That way, only one VCR would be necessary to provide the second channel. Modifying the TV set would involve breaking the audio and video signal paths at the appropriate points so that the PIP unit can be interposed. Fig.2 shows the block diagram of the TV PIP Unit which can be divided into audio and video sections. The audio section (IC5, IC6a, IC6b & IC6d) accepts the stereo inputs from the VCRs and produces a single output (AUDIO OUT) which may be switched bet­ ween either VCR or muted. In addition, the left and right chan­nels of the selected source are mixed to produce a mono signal which is fed to the video modulator audio input. The video outputs from the VCRs are fed to the video inputs of the PIP board. The output from this board is either video 1, video 2 or a picture-in-picture signal. This output is then split two ways. First, it is buffered by driver stage Q4 to provide the video output signal. And second, it is fed to the video modulator which produces the alternative RF output signal. As mentioned before, the remote transmitter controls all the functions of the PIP unit. The PIP button switches the picture-in-picture display on or off, while the SWAP button below it switches the PIP and full-screen channels (the audio automati­ cally swaps as well). You can also use the adjacent audio SWAP button to switch the sound from the main picture to the PIP, or vice versa. The ROTATE button selects which corner of the screen plays host to the PIP. This button sequentially moves the PIP display anticlockwise to the next corner of the screen each time it is pressed. Finally, as its name implies, the MUTE button kills the audio. The signals from the remote control unit are picked up by a remote control receiver circuit which is based on IC1. Its output is then fed to the control logic block (IC2-IC4) and this in turn controls the audio switching and the PIP board. Fig.1: the PIP Unit accepts video and audio signals from two VCRs. The processed output from the PIP Unit is then fed to the TV set, either via the antenna socket or via video and audio inputs (if fitted). Circuit details – transmitter Fig.3 shows the circuit for the IR Transmitter. IC1 is an SM5021B encoder which outputs a unique code for each switch. This code gates a 38kHz carrier on and off and the output at pin 15 then drives Darlington transistor pair Q1 & Q2. These in turn drive IRLED1 via a 4.7Ω current limiting resistor. The 38kHz carrier is derived by dividing the 455kHz oscillator frequency at pins 12 & 13 by 12. LK1 and LK2 are included to alter the coding for each switch. This will Fig.2: block diagram of the PIP Unit. The PIP board (bottom, centre) processes the video signals from the two VCRs and produces a single PIP signal. It also controls the logic circuitry which switches the audio signals from the two VCRs. April 1997  13 Fig.3 the circuit for the IR Transmitter. IC1 is an SM5021B encoder which outputs a unique code for each switch. This code gates a 38kHz carrier on and off and the output at pin 15 drives Darlington transistor pair Q1 & Q2. These in turn drive IRLED1. avoid conflict with another remote control which uses the same device. Normally, these can both be left open for the default coding. Connecting either or both pins 1 & 2 of IC1 to ground will change the code. Circuit details – PIP unit Refer now to Fig.4 for the circuit details of the PIP Unit. It’s designed around the PIP board which, as mentioned above, comes as a pre-built module. Starting at the top lefthand corner, IRD1 picks up the signals from the handheld transmitter. This 3-terminal device is actually a bit more complicated than it looks. It contains an IR receiver diode, an amplifier tuned to 38kHz, a 38kHz bandpass filter, an automatic gain control (AGC) section Specifications Video Picture-in-picture size .............................Less than 1/6th full screen Video output ...........................................1Vp-p (adjustable) Modulator output ....................................Channel 0 or 1 mono audio Audio (wrt 100mV in or out) Frequency response ...............................-0.25dB at 10Hz & -1dB at 60kHz and a detector. Its output is a digital pulse train identical to that generated by the transmitter but inverted. Q1 is used to re-invert the signal, after which it is fed to pin 2 of decoder IC1 (SM5032B). The decoding links LK1 and LK2 must match those in the transmitter, to ensure compatibility. IC1 has eight outputs (A-H) and these match the switches in the transmitter. In this circuit, however, we only use the A, B, C, E & F outputs which are all momentary action. Pressing the ROTATE (A) switch on the transmitter will produce a high output on the ‘A’ output of decoder IC1. Similar­ ly, pressing the other buttons on the transmitter produces highs on the other decoder outputs. The ‘C’ output (PIP) of IC1 drives the clock input of flip­flop IC2a. Each time ‘C’ goes high, IC2a’s Q output (pin 1) toggles (low to high or high to low). When this output goes high, the output of Schmitt NAND gate IC3d goes low. This selects the picture-in-picture function for the PIP board. The ‘A’ output (ROTATE) of IC1 is buffered by gates IC3a & IC3b. When the ‘A’ output goes high, the inputs to IC3c are pulled high via the .012µF capacitor and IC3c’s output goes low. After about 120µs, the capacitor charges via its associated 10kΩ resistor and so IC3c’s output goes high again. As a result, IC3d delivers a 120µs high-going pulse to the PIP input of the PIP board (assuming that pin 8 of IC3d is high). This short pulse instructs the PIP board to rotate the picture-in-picture display to the next position on the screen. The pulse duration is not critical by the way and can be anywhere between 1µs to 10ms for the rotate function to work correctly. The ‘B’ output of IC1 drives a second flipflop designated here as IC2b. This also toggles its Q output (pin 13) at each positive going pulse to Total harmonic distortion ........................< 0.01% from 20Hz to 20kHz Signal-to-noise ratio ������������������������������78dB wrt 100mV & 20Hz to 20kHz filter with input unloaded; 88dB wrt 100mV & 20Hz-20kHz filter with input loaded by 1kΩ resistor Crosstalk between any two channels .....-56db worst case at 10kHz Maximum signal handling .......................3V RMS Signal gain .............................................0dB (x1) 14  Silicon Chip Fig.4 (right): the signals from the handpiece are picked up by IRD1 and decoded by IC1. The decoded outputs then drive the PIP module via logic circuitry. CMOS analog switch IC5 switches the audio signals and is controlled by IC1 via flipflops IC4a & IC4b and transistors Q1 & Q2. The modulator produces an RF output signal on either CH0 or CH1.  Mute level ...............................................-63dB April 1997  15 Fig.5: install the parts on the PC board as shown in this wiring diagram. Note that the two links shown dotted are mounted on the main board beneath the PIP module. TABLE 1:RESISTOR COLOUR CODES  No.    2    1  14    1    2    3    7    1    2    1    1 16  Silicon Chip Value 100kΩ 39kΩ 10kΩ 5.6kΩ 4.7kΩ 2.2kΩ 1kΩ 180Ω 100Ω 75Ω 4.7Ω 4-Band Code (1%) brown black yellow brown orange white orange brown brown black orange brown green blue red brown yellow violet red brown red red red brown brown black red brown brown grey brown brown brown black brown brown violet green black brown yellow violet gold brown 5-Band Code (1%) brown black black orange brown orange white black red brown brown black black red brown green blue black brown brown yellow violet black brown brown red red black brown brown brown black black brown brown brown grey black black brown brown black black black brown violet green black gold brown yellow violet black silver brown Use the shielded cable and the connectors supplied with the PIP module to make the connections to the main board. A small round piece of red Perspex is fitted to the front panel to provide a window for the infrared receiver (IRD1). the clock input. In this case, the Q output drives the SWAP input of the PIP board. This instructs the PIP board to swap the main picture with the PIP. When power is first applied to IC2a and IC2b, their reset inputs (pins 4 & 10) are pulled high via a 10µF capacitor. This resets their Q outputs low. The 10µF capacitor then charges via its associated 100kΩ resistor, so that the resets are released after about one second. The low Q outputs ensure that the power on default settings for the PIP board are: (1) PIP off; and (2) Video Input 1 selected. The ‘B’ output of IC1 also drives the clock input of flip­flop IC4a, via diode D1. This swaps the audio channel whenever the video swap function is enabled. Similarly, the ‘E’ output of IC1 also drives IC4a’s clock input, this time via diode D2, to perform the audio swap function. Let’s see how this all works. As shown, the output of IC4a drives transistor Q2 via a 10kΩ resistor. This transistor effectively inverts and level shifts the 5V signal from IC4a to a 12V signal which is then applied to pin 10 of IC5. IC4b and Q3 function in exactly the same fashion. In this case, however, the clock (CK) input of IC4b is driven by the ‘F’ output of decoder IC1. The level shifted output appears at Q3’s collector and is fed to pin 9 of IC5. Audio switching IC5 is a 4052 CMOS analog switch. It is basically a 2-pole 4-way switch which is controlled by the signals on its A & B inputs (pins 9 & 10). When A & B are both low, the X0 and Y0 inputs are selected and fed The switches on the PIP module must be set exactly as shown here; ie, two switches down, the rest up. through to the X and Y outputs (pins 13 & 3). Similarly, if A is high and B is low, the X1 and Y1 inputs are selected. And if B is high, either X2 or X3 and either Y2 or Y3 are selected, while X0, X1, Y0 and Y1 are all open. Note, however, that inputs X2, X3, Y2 & Y3 are all connected to­gether and biased to half supply (V/2). They are also AC-coupled to ground via a 10µF capacitor. If B is high, X2 & X3 are connected to the X output, while Y2 & Y3 are connected to the Y output. The left and right audio signals from VCR 1 are fed to the X0 & Y0 inputs of IC5, while those from VCR 2 are fed to the X1 & Y1 inputs. Each input is AC-coupled via a 10µF capacitor and biased to half supply via a 10kΩ resistor. In addition, a 1kΩ resistor is included in series with each input to provide current limiting. If A & B are both low, it follows that the signals from VCR 1 are fed through to the X & Y outputs of IC5. Similarly, if A is pulled high (ie, Q2 switches off), the signals from VCR 2 are fed through instead. And finally, if B is pulled high, no input signals are selected and the X and Y outputs are shunted to ground via the 10µF capacitor connected to X2, X3, Y2 & Y3; ie, the audio is muted. When power is first applied, flip­ April 1997  17 The various inputs and outputs are all run via RCA sockets at the rear of the unit. Note that the power supply socket must be insulated from the rear panel if a metal label is used. flops IC4a & IC4b are set via the 10µF capacitor connected between their Set inputs (pins 8 & 6) and the +12V supply rail. This sets the Q outputs high and the collectors of Q2 and Q3 low. Thus at power up, the audio signals from VCR 1 are selected and the muting is off. The left & right audio signals from IC5 are buffered using op amps IC6a and IC6b. The outputs from these stages appear at pins 7 & 14 respectively and are fed to the output sockets via 100Ω resistors and 10µF capacitors. In addition, the left and right channels are mixed via 10kΩ resistors and fed to amplifier stage IC6d. Its pin 14 output in turn drives the audio input of the modulator via a 10µF capaci­tor. VR1 provides a level setting adjustment. PIP board While we do not propose to describe in detail how the PIP board works, we can give a precis of its operation. A video signal consists of luminance (brightness) and chromin­ance (co­lour) information, mixed with colour burst and line and frame sync pulses. The line sync pulses indicate the beginning and end of each line in the picture; ie, from the far left to the far right of the TV screen. The video luminance and colour signals are present between these sync pulses and produce the picture information in each line. The frame sync pulses indicate the beginning and end of a Where To Buy The Parts The major parts for this design are available as follows: (1) PIP module plus main PC board: Av-Comm Pty Ltd, PO Box 225, Balgowlah, NSW 2093. Phone (02) 9949 7417; Fax (02) 9949 7095. Price – $209 plus $10 p&p. Please quote Cat. K1400 (available end of May 1997). (2) Complete IR transmitter kit plus all IR receiver parts (please specify no PC board for receiver when ordering): Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3563; Fax (02) 9584 3561. Price $30 plus $3.50 p&p. (3) Astec UM1285AUS 0/1 video modulator: Dick Smith Electronics (Cat. K-6043). 18  Silicon Chip complete picture. In order to shrink the full-sized picture into a PIP size, the line sync information must be altered so that the picture is positioned on a different part of the screen. This is done in two ways. First, the line length for the PIP is reduced by discarding some of the video information so that it fits into a smaller space. And second, the num­ ber of lines is reduced to decrease the picture height. The way in which this is done is rather complicated. First, the required information for each video frame is sampled using a fast A-D converter and stored in a dual-port RAM. The term “dual-port” simply means that we can simultaneously store information in memory and retrieve it, without halting either process. The stored video information is then retrieved from the memory at the appropriate rate, reconverted to analog format and inserted into the main (full-screen) video signal. Basically, all we are doing is substituting PIP video infor­mation over part of each line for the main picture, until the PIP is complete. Because of this, the information retrieved from the RAM does not contain vertical or horizontal sync pulses, since these would upset the operation of the main picture. The video output from the PIP board goes to two separate circuits: (1) a buffer stage based on transistor Q4; and (2) to the modulator. VR2 sets the video level into the base of Q4. This transis­tor is wired as an emitter follower and the resulting signal is coupled to the video output socket via a 470µF capacitor. The 75Ω emitter resistor sets the output impedance. VR3 sets the input level for the video modulator. This modulator provides an RF output on either channel 0 or 1, depend­ing on the channel select linking option. Power to the modulator is derived from the +12V rail via a 180Ω current limiting resis­tor. Power supply Power for the circuit is derived from a 12VAC plugpack. It’s output is fed to bridge rectifier D3-D6 and filtered with a 2200µF capacitor to derive a 16VDC (nom.) supply. This is then applied to 3-terminal regulator REG1 which provides a 12V supply rail for the PIP board and ICs 5 & 6. A 3-terminal regulator on the PIP board provides a separate +5V rail and this is used to power IRD1 and ICs 1-4. It also drives a LED power indicator via a 560Ω resistor. Finally, a half-supply voltage is derived from a voltage divider consisting of two 10kΩ resistors. This is buffered by unity gain amplifier stage IC6c and the resulting V/2 output used to bias the audio input signals to IC5. Construction The parts for the PIP Unit are mounted on a PC board coded 02302971 and measuring 197 x 154mm. This board accommodates the preassembled PIP module, the modulator and all the support cir­cuitry. You can buy the PIP module and the PC board from Av-Comm Pty Ltd, while the handheld transmitter and receiver parts are available from Oatley Electronics. Dick Smith Electronics stocks the specified video modulator. Fig.5 shows the parts layout on the PC board. Before mount­ ing any of the parts, check the board carefully for shorts bet­ween the tracks and for breaks in the copper pattern. You should also check that the mounting holes for the PIP board and for REG1 are drilled to 3mm and that the mounting holes for the modulator earth lugs are correct. Begin the assembly by installing the links and the resis­tors. Note that two of the links are shown dotted, to indicate that they go under the PIP module – don’t forget these. Table 1 PARTS LIST 1 PC board, code 02302971, 197 x 154mm 2 self-adhesive labels for front & rear panels, 215 x 34mm 1 remote control transmitter label, 31 x 63mm 1 plastic case, 225 x 165 x 40mm (Jaycar Cat. HB5972) 1 PIP board (from Av-Comm) 1 video modulator, Astec UM1285AUS 0/1 (DSE Cat. K-6043) 1 12VAC 500mA plugpack 2 2 x 2-way PC-mount RCA sockets (Altronics P-0211) 1 RCA panel-mount socket 1 DC panel socket to suit plugpack 1 SPDT toggle switch (S1) 1 TO220 heatsink, 19 x 19 x 6mm 1 50kΩ horizontal trimpot (VR1) 2 1kΩ horizontal trimpots (VR2,VR3) 1 400mm length of 0.8mm tinned copper wire 1 500mm length of hook-up wire 4 self-tapping screws to secure board to case 4 3mm dia. x 9mm screws & nuts 4 5mm spacers 1 3mm dia. x 6mm screw and nut 1 8mm ID grommet (to insulate DC socket) 15 PC stakes 1 10mm dia. x 3mm red Perspex for IR sensor window Semiconductors 2 4013 dual-D flipflops (IC2,IC4) 1 4093 quad Schmitt NAND gate (IC3) 1 4052 dual 1-to-4 analog multiplexer/demultiplexer (IC5) 1 TL074, LF354 quad op amp (IC6) 1 7812 12V 3-terminal regulator (REG1) 3 BC548 NPN transistors (Q2, Q3, Q4) 2 IN914, 1N4148 signal diodes (D1,D2) 4 1N4004 1A diodes (D3-D6) 1 3mm LED (LED1) Capacitors 1 2200µF 16VW PC electrolytic 1 470µF 16VW PC electrolytic 1 47µF 16VW PC electrolytic 1 22µF 16VW PC electrolytic 14 10µF 16VW PC electrolytic 1 .012µF (12n or 123) MKT polyester Resistors (0.25W 1%) 2 100kΩ 5 1kΩ 13 10kΩ 1 180Ω 1 5.6kΩ 2 100Ω 1 4.7kΩ 1 75Ω 3 2.2kΩ 8-Channel IR Transmitter 1 Magnavox remote control handpiece (includes IRLED and battery clips) 1 455kHz resonator (X1) 1 PC board 2 AAA cells 2 PC stakes Semiconductors 1 SM5021B encoder (IC1) 1 BC548 NPN transistor (Q1) 1 C8050 NPN transistor (Q2) Capacitors 1 10µF 16VW PC electrolytic 2 100pF (100p or 101) ceramic Resistors 2 1kΩ 1 4.7Ω 8-Channel IR Receiver 1 SM5023B remote control receiver (IC1) 1 BC338 NPN transistor (Q1) 1 PIC12043 infrared receiver (IRD1) Capacitors 1 10µF 16VW PC electrolytic 1 .001µF (1n0, 102 or 1000p) ceramic Resistors 1 39kΩ 1 10kΩ 1 4.7kΩ April 1997  19 RF OUT + + MUTE + AUDIO + ROTATE + VIDEO PICTUREIN-PICTURE REMOTE CONTROL SWAP SWAP + PIP Fig.7: the full-size artwork for the rear panel. It can be photocopied and affixed to the rear panel using double-sided adhesive tape. AUDIO OUT IN2 IN1 12VAC IN + R + VIDEO IN 2 + R + + L + VIDEO IN 1 + VIDEO OUT Fig.6: this full-size artwork can be used as a drilling template for the front panel. POWER + + + + L + + TV PICTURE-IN-PICTURE Fig.8: this is the full-size front panel artwork for the hand-held transmitter. lists the resistor colour codes but it is also a good idea to check each value using a digital multimeter, just to make sure. The diodes can be mounted next, taking care to ensure that they are oriented correctly. Note that two types are used on the main PC board: (1) the 1A 1N4004s which have a black body; and (2) the smaller 1N914s which are usually orange in colour. The 14 PC stakes can now be installed on the PC board, followed by the ICs. Take care with the orientation of each IC and check that the correct type has been installed at each loca­tion before soldering. Note particularly that IC1 & IC6 are oriented differently to the other ICs. The LK1 and LK2 linking options for IC1 can be left open circuit, unless you already have an identical IR remote control with the same coding. The four transistors are all BC548 types and these must be oriented exactly as shown. REG1 is mounted horizontally, with its leads bent at rightangles so that they pass through the PC board. It is fitted with a small heatsink and bolted to the PC board using a 3mm screw and nut. The capacitors can now be installed, along with IRD1, LED1 and the trimpots. Be sure to orient IRD1 with its bubble-shaped lens towards the front. LED1 should be mounted at full lead length, so that it can later be bent over and pushed through its mounting hole in the front panel hole. The two RCA socket sets must have their plastic locating pins removed before they are mounted. Remove these using sidecut­ters, then solder the RCA sockets in position, taking care to ensure that their bottom surfaces sit flush with the board. The video modulator is mounted in the top righthand corner of the board. As shown, the unit is wired for channel 0. If you want channel 1, simply transfer the lead from the CH0 position to the CH1 position. The PC board assembly can now be completed by mounting the PIP module. This board is mounted on 5mm spacers and secured using 3mm screws and nuts. Wire up the board using the supplied shielded leads and the red/black power lead. Don’t forget to solder a length of hookup wire from the onboard 5V regulator output to the +5V PC stake on the main PC board. Final assembly The completed assembly is housed in a standard plastic instrument case measuring 225 x 165 x 40mm. 20  Silicon Chip The infrared transmitter should only take a few minutes to assemble. Notice how the two transistors are bent over, so that they sit flat against the board. The board simply clips into position in the case. Begin the case assembly by affixing the labels to the front and rear panels. This done, drill out the holes on the rear panel for the RCA sockets, the power socket and the RF OUT socket. The best way to go about this is to first drill small pilot holes and then carefully enlarge each hole to the correct size using a tapered reamer. Moving now to the front panel, drill the holes for the power switch and its adjacent indicator LED. You will also have to drill a 10mm hole in the front panel in line with IRD1. We fitted a 10mm-dia. red Perspex window to this hole, rather than simply leave it open. The various items can now all be mounted in posi­tion and the wiring completed as shown in Fig.5. Note that the PC board assembly is secured using self-tapping screws which go into integral pillars in the base of the case. Two small self-tapping screws are also used to secure the stereo RCA sockets to the rear panel. Important: if a metal label is used on the rear panel (eg, Dynamark), be sure to insulate the power socket from the panel. This can be done by stripping back the label from around the mounting hole and then fitting a large insulating washer under the mounting nut. If this is not done, the metal label will short one side of the 12VAC power supply to ground. Transmitter assembly Very little work is required to assemble the IR transmitter, as Fig.9 shows. It’s mainly a matter of soldering a few parts to the transmitter board. Take care to ensure that the infrared LED is installed with the correct polarity and note that Q1 is a BC548 while Q2 is a C8050. After that, all you have to do is attach the label to the transmitter case and cut out the holes for the switch pads, as marked. You will also have to cut off the switch pads on the rubber membrane that were originally intended for the volume and CD selections. The two halves of the case are simply clipped together after installing the two 1.5V AAA cells. Testing Now for the smoke test but first go back over your work carefully and check for possible wiring errors. In particular, check that all components are correctly oriented and that the correct part has been used at each location. This done, apply power and check that there is +12V at the output of REG1 and +5V at the output of the regulator on the PIP board. If these voltages are OK, switch off and set two of the DIP switches on the PIP module to the down position, as shown on Fig.5. These select the video sources for the main and PIP display. It’s now simply a matter of connecting the unit as shown in Fig.1 and testing it for correct operation. Remember to tune the TV set to the appropriate channel (either CH0 or CH1), if you are using the RF output from the PIP Unit. Of course, this step will not be necessary if you are feeding the audio/video outputs from the PIP Unit to the TV set. Now apply power and check that the signal applied to INPUT 1 appears on the screen as the main picture. At this stage, there should be no PIP. If this is correct, adjust VR3 to obtain the correct contrast range and to prevent Fig.9: take care with the orientation of the infrared LED and don’t confuse transistors Q1 & Q2 when installing the parts on the transmitter board. The two transistors are installed flat against the board as shown in the photo at the top of the page. overmodulation (assum­ ing the RF output is being used). If the direct video output is being used, adjust VR2 for correct contrast instead. VR1 is adjusted for a normal sound level. You can now check the remote control. Select PIP and check that a small picture corresponding to the second video input appears in the lower righthand corner of the screen. If it does, check that the ROTATE and video SWAP functions work – the sound should follow the main picture. Finally, check that the audio SWAP SC and MUTING functions work. April 1997  21