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Build a colour TV pattern generator, Pt.2 This month, we describe construction of our new colour TV pattern generator. This is made easy since most of the components are on a single PC board and there is only one setting up adjustment. By JOHN CLARKE The Colour TV Pattern Generator is housed in a standard plastic instrument cas e measuring 205 x 158 x 62mm. All of the space on the floor of the case is taken up by a large singlesided PC board measuring 17 5 x 142mm and coded SC02210911. It has quite a few wire links on it but we opted for this arrangement because a double-sided board would have been 68 SILICON CHIP considerably more expensive. There are two toggle switches, one rotary switch and a LED on the front panel, while the rear panel carries a power input socket (for an external 12VAC plugpack), a direct video output socket (RCA type) and the RF output from the modulator (also an RCA socket). There are two types of modulator recommended for this project. One mounts directly onto the PC board while the other, a slightly larger model, is ,trapped onto the rear panel and linked to the PC board with short wires. More on these later. You can begin construction by carefully checking the PC board pattern against the artwork published in this article. Check for shorted, open circuit or missing tracks. Ensuring that the p.attern is free from errors at this stage can save a lot of time and frustration later on. Now test the PC board for correct fit inside the case. It should easily fit on the floor of the case, with the mounting holes lining up with the integral plastic standoffs. Make sure that these mounting holes are large enough to accept the self-tapping screws sup- HOLE FOR MODULATOR OUTPUT ORFOUTPUT VIDEO MODULATOR VM41'6/A2E3 GND S3 ~ S1 ~ REAR PANEL PC stakes and links The first step in the construction is to install PC stakes at the 14 external wiring points (see Fig.4). Make sure you heat the pins well with your soldering iron before tinning them with the solder. If you are not careful with this step, it is quite easy to end up with dry joints on the PC stakes. Next to go in are the wire links and there are quite a few of these, all using tinned copper wire (in our case, 0.71mm in diameter). Before cutting the links to length, it is a good idea to straighten the wire. This can be done by clamping one end of the wire in a ---::f':) LED1 13,.-- A FRONT PANEL Fig.4. use this diagram in conjunction with the circuit diagram published last month when assembling the pattern generator. Note that the HC CMOS ICs are easily damaged by static electricity, so be sure to observe the precautions described in the text. plied and check that the modulator mounting holes in the PC board are large enough to accept the mounting pins. K 14 vice and then pulling the other end with a pair of pliers until the wire stretches slightly. Make sure that all the links are dead straight and parallel, to avoid short circuits. Next, install the resistors and diodes. Be careful with the orientation of the diodes and check that the correct type is installed at each position. There are three types of diodes used in the circuit. The black diodes with the silver stripe on one end are the rectifier types used for D1-D4. Diodes D5-D9 are small signal diodes which are clear-bodied with orange internals. The final diode is ZDl, a zener diode. Watch out for static The !Cs can now be installed but take care with static discharges when you are installing the CMOS devices. If the weather is very dry and your room is carpeted, it is highly likely that you will have a problem with static discharges. This can certainly blow !Cs in this circuit (we blew a couple ourselves). The way to avoid this problem is to earth the barrel of your soldering iron and then conn ect it via a jumper lead to the OV pattern on the PC board. After that , you need to earth yourself. Use a wrist strap (or a jumper lead connected to your metal watch band) to connect yourself to the OV pattern on the PC board. Finally, avoid touching the pins of the !Cs when mounting them on the board and solder their supply pins first. The capacitors, trimmer capacitor VCl and the crystals can now be installed. Note that the electrolytic capacitors must be correctly oriented, as shown on the overlay diagram . Also, be sure to · use the correct crystal at DHY .\ /ll/•:/l 1991 69 ,_ ___ \ ,_----'--- - This version of the pattern generator uses the VM416/A2E3 modulator which is mounted directly on the PC board. Take care with the wiring to the pattern selector switch, as it's easy to make a mistake here. each location on the board. The board assembly can now be completed by installing the two 3terminal regulators and transistor Ql. Note that REGl is a 7812 device while REG2 is a 7805. Two modulator types As noted above, there are two recommended video modulators for the Colour TV Pattern Generator. The first is the VM416/ A2E3 which mounts directly onto the PC board and is available from Dick Smith Electronics. The second typ e is the HL-RM-TS3/4AU which mounts on the rear panel and is available from Jaycar Electronics. If you are using the VM416/ A2E3 modulator, solder its mounting lugs to the copper pads on the PC board using a heavy-duty soldering iron. The remaining two leads from the modu70 SILICON CI-IIP lator solder into the PC board to make the INPUT and V+ connections. If you are using the HL-RM-TS3/ 4AU modulator, insert 100mm lengths of insulated hookup wire into the GND, INPUT and V+ locations on the PC board for connection to the modulator later on. Drilling the panels Work can now begin on the case. You will need to drill holes in the front and rear panels to accommodate the switches and sockets. The Dynamark label can be used as a template for marking the drilling positions on the front panel. After the holes have been drilled and deburred, the label can be stuck to the front panel and the holes cut through it with a sharp utility knife. The rear panel requires holes for the power input socket, the RCA video output socket and a large hole for the video modulator output socket. If the HL-RM-TS3/4AU modulator is used, it should be mounted upside down in the top corner of the rear panel, as shown in the photographs. Drill holes for the RCA output socket and for a ca:)le tie to clamp it to the rear panel. Alternatively, the hole position for the on-board VM416/A2E3 modulator can be found by temporarily positioning the rear panel and the PC board in the case. Drill a small pilot hole initially, then ream the hole out to clear an RCA plug. Installation & wiring Once all the holes have been drilled, mount the various hardware items on the panels, then install the panels and the PC board in the case. Fig.4 shows the wiring details. Use various colours of hookup wire or rainbow cable for the wiring to the LED and switches. By using different col- BUILD YOUR OWN FAX/MODEM This is a fully featured kit The Comma Fax/Modem is a commercially designed kit you can build. It will turn your PC (or Macintosh) into both a fax machine which can transmit faxes up to 9600 baud, as well as a Modem which su pports both 1200 and 2400 baud. You get all the necessary components as well as a professional case, and power supply. You also receive FREE Fax/Modem software. All this for less than $300. The Comma Fax/Modem uses the latest technology in digit al signal processing to ensure lasting troublefree operation. 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NSW2066 PRICES CURRENT FOR MONTH OF PUBLICATION OR WHILE STOCKS LAST e SERVICE IS THE DIFFERENCE e [Z] [BI SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE shorts and incorrectly placed or oriented components. Assuming that you get the correct reading, check that the output of REG 1 is somewhere between +11.4V and +12 .6V. Once again, switch off immediately if you find anything amiss. Now you can check that power is being applied to all the ICs. There should be +5V on the positive supply pin of every IC, except for IC16 which operates at +lZV. Finding the positive supply pin for all the 74HC series ICs is easy since it is always the highest numbered pin. Of the remaining two ICs, IC14 should have +5V on pin 8 while IC16 should have +lZV on pin 11. The alternative HL-RM-TS3/4AU modulator is mounted upside down on the rear panel and secured using a plastic cable tie. Its various terminals are then connected to the PC board using short lengths of hookup wire. ours, you will be able to easily identify each lead when it comes to checking the wiring later on. Be sure to use medium-duty hookup wire for the power switch (Sl) wiring. Finally, if you are using the HLRM-TS3/ 4AU modulator, the terminal closest to the rear panel connects to the INPUT (composite video) terminal on the PC board. The next terminal connects to the V+ terminal on the PC board, while the GND wire from the PC board is soldered to the case of the modulator. The remaining two inputs on this modulator are left unconnected. Cut the wires to these inputs short so that they are unable to contact the modulator case. If everything checks out, the pattern generator can now be checked on a TV set. To do this, connect a lead between the video modulator output and the RF input to your TV set and either tune to channel 2 for the VM416/ AZE3 modulator or to channel 4 for the HL-RM-TS3/4AUmodulator. Now Testing The pattern generator is now ready for testing. Plug the 12V AC plugpack lead into the power socket and set your multimeter to read 0-Z0V DC. Connect the negative lead of the multimeter to the metal case of the modulator and the positive lead to the output of the +5V regulator (REG 2). Apply power and check that the voltage reading on the multimeter is between +4.75V and +5.25V. If not, switch off immediately and check the PC board for faults such as solder CAPACITOR CODES 0 0 0 0 0 0 0 0 0 Value IEC Code EIA Code 0.1µF .01µF 330pF 220pF 100pF 82pF 33pF 5.6pF 100n 10n 330p 220p 100p 82p 33p 3p3 104 103 331 221 101 82 33 3.3 RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 72 No. Value 4-Band Code 5-Band Code 1 1 9 10MQ 36kQ 10kQ 5.6kQ 2.2kQ 1kQ 910Q 470Q 390Q 330Q 100Q brown black blue gold not applicable brown black orange gold green blue red gold red red red gold brown black red gold not applicable yellow purple brown gold orange white brown gold orange orange brown gold brown black brown gold brown black black green brown orange blue black red brown brown black black red brown green blue black brown brown red red blpck brown brown brown black black brown brown white brown black black brown yellow purple black black brown orange white black black brown orange orange black black brown brown black black black brown 1 3 1 1 2 SILICO N CHIP CI-118A 20MHz Dual Trace Osc;l.ll◄~ SPECIFICATIONS: Operating modes Yl, Y2, Yl and Y2 added are switchable alternately and lnterml ttently. Bandwidth, MHz: ■ DC coupled input: at -3dB .. 0-20 ■ DC coupled input: at -6dB .. 0-35 ■ AC coupled input: at -3dB .. 3x10·'-20 ■ AC coupled input: at -6dB .. 2x10·'-35 ■ input with external divider in position 1:1 .. 0-7.0 Transient response built-up time, ns, max.: ■ ■ DC coupled input: .. 17.5 with external divider in position 1:1 .. 50 Deflection factor (11 calibrated steps with 1-2-5 seq.) ■ ■ ■ mV /DIV: Accuracy,%: Max. input (AC/DC) V: .. 5-10' .. +/ - 4 .. 250 Input Impedance, Mohm/pf: ■ ■ ■ DC coupled input: with external divider in position 1:10 with external divider In position 1:1 .. 1/20 .. 10/15 .. 1/100 Sweep speed (21 calibrated steps with 1-2-5 seq.) ■ ■ ■ ns/ DIV: Accuracy,%: 50ns/ DIV+ Accuracy, %: 20ns/ DIV .. 20-50x10' .. +/- 4 .. +/ - 8 Trigger modes: ■ Autq, turning to triggered upon application of trigger signals HOPM (NORM). Trigger source: ■ Dimensions: 212 x 133 x 336mm Screen Size: 4" Includes 2 x 1:1 10:1 probes, and screen protection cover. Internal (from channe l Yl or Y2), external. Sensitivity for Internal s"9nchronlzation, V: ■ ■ 50Hz to 4MHz, DIV., Max.: .. 0.8 4MHz to 20MHz, DIV, Max.: .. 2 Sensitivity for external synchronization, V, Max.: ■ lOHz to 20MHz .. 0.2 Typical external synchroniz ation ■ Input imp. kohm/pf A.C.N . 001-372-372 .. 70 / 15 Note: for Go vernment Dept's, Schools, Sales Tax No. holders, etc only $430.43 ea. (ex-tax) - official order must be produced + DOT HATCH CHECK......____\ I / WHITE COLOUR RED / + - BARS------,GREYSCALE + POWER - =IIJI/JIIPCOLOUR TV PATTERN GENERATOR PATTERN Fig.5: this is the full size artwork for the front panel. fine-tune the TV set until the pattern selected is displayed on the screen. At this stage, colour may not be present because the colour burst frequency may need tweaking. Select the red raster pattern and adjust VC1 so that the screen is red. If you are using a metal-tipped alignment tool (better than a small screwdriver), you will need to remove it from VC1 after each adjustment to allow the crystal to oscillate correctly. The final setting for VC1 should be midway between the two positions where the colour drops out. This group of composite video waveforms is presented for those needing to troubleshoot the pattern generator. Below left is the colour bar signal while to its right is the equivalent grey scale signal. The waveforms on the facing page show the crosshatch signal (left) and the white raster signal (far right). 74 SILICON CHIP That completes the assembly. If all the patterns can be displayed on the screen, then your work is finished and you have a very useful service instrument for your workshop . Troubleshooting If it doesn't work, first check for incorrect wiring or component placeThe colour burst frequency is adjusted ment. The underside of the PC board by tweaking trimmer capacitor VC1 should also be checked for shorted until a red raster appears (see text). tracks, dry joints and open circuits. Make sure your wiring to the pattern selector switch is correct, as it is fairly kit projects do not usually malfunceasy to make a mistake here. . tion, the HC CMOS ICs specified in this If these checks do not find the probcircuit are more fragile than ordinary lem, then you will probably need acCMOS ICs . As pointed out earlier, they cess to an oscilloscope to check the are easily damaged by static electricwaveforms. Fig.1 in the November ity. If you are prodding about in the 1991 issue shows the main waveforms circuit, remember to wear a wrist strap. generated by each circuit block. Don't write off an IC before you By checking the waveforms at varihave thoroughly checked the solder ous points in the circuit, it shoul d be connections to its pins. Poor solderpossible to isolate the section which ing to IC pins and incorrectly wired is not functioning correctly. switches are the most common probNote that while the ICs supplied in lems in malfunctioning kits. r. ~~ ..-----n...._ . ~.~~ ~r Finally, there are two changes to the parts list and circuit from last month. First, the video modulator can be either a VM416/A2E3 or a HL-RM- ~~ TS3/4AU. Second, the 680Q resistor shown on the circuit (Fig.3) in series with the 6.8V zener diode (ZDl) should be changed to lOOQ. SC Fig.6: here is the full size artwork for the PC board. Check your board carefully against this pattern & repair any defects before mounting any of th e parts. DECEMBER1991 75