Pinouts for the Wells-Gardner NTSC Decoder Ruben Panossian ------------------------------------------ This decoder is made on a small square PCB and has the model number DY-1-0 at the end of the PCB with the corner cut off. There are two basic revisions, 85X0172 (P371) and 85X0311 (P600). Pinouts: -------- P204: 1 - Vcc * 2 - Vcc * 3 - GND 4 - Key 5 - Blanking Input P203: 1 - Positive composite Sync out ** 2 - Key *** 3 - GND 4 - Video Blue out 5 - Video Green out 6 - Video Red out Notes: * The Vcc is dependant on the revision of the PCB. The earlier revision PCBs (P371) have a Vcc of +15V DC. The newer revision PCBs (P600) have a Vcc of +12V DC, although, +12V still works with the earlier (P371) revision PCBs. The difference between the two versions is with R256. It is used to lower the voltage from +15V to +12V, on the earlier revision PCBs. The newer PCBs, using regulated power supplies as Vcc source, just have a wire link in the place of the resistor. The newer revision also did not have the over voltage protection circuit (components not installed) as the Vcc was intended to be supplied from a regulated power supply. ** This pin will have negative Sync output on it after the modification *** This pin was used to supply +12V and blanking in some (modified) versions. They were altered to suit some games, so take note when using an old revision decoder. How can I use this NTSC decoder in my JAMMA cabinet? ---------------------------------------------------- To enable this decoder to be used with a JAMMA cabinet, without modifying the harness or monitor chassis, the NTSC decoder needs to be modified. After completing the modifications use +12V DC as the Vcc supply for the NTSC decoder. The following parts will be required for the modification: 1 x 2N3904 transistor 1 x 3.9K resistor 1 x 4.7K resistor 1 x 3.3K resistor 50mm of wire 50mm of 3.2mm heat shrink tubing Procedure: ----------- Note: All references are to the solder side of the PCB unless otherwise noted. Read the entire step before proceeding with it. Pinouts of the 2N3904 transistor: while looking at the transistor with the ID lettering right side up (legs facing downwards) the left leg is the Emitter, the middle leg is the Base, and the right leg is the Collector. Take care when locating components on the PCB, as the part IDs are close to adjacent parts and it would be easy to incorrectly identify a part. Step 1. Cut the middle leg of the 2N3094 transistor leaving approximately 5mm (1/4"). Do the same with one end of the 4.7K resistor. Step 2. Solder the short end of the 4.7K resistor to the Base (middle leg) of the 2N3904 transistor. It is easy to do if you first tin both the transistor and resistor ends with solder, then put both ends together and heat. Step 3. Cover the middle leg of the transistor and resistor with heat shrink tubing to about 5mm (1/4") covering the other lead of the resistor. Heat the heat shrink tube. Step 4. Locate R256. There will either be a resistor or a wire link installed. If there is a resistor installed, remove it and install a wire link. Step 5. Locate Q204 (2N3906). Near Q204 is a black wire (on the parts side) which is soldered onto the PCB, between R224 and R223. On the solder side of the PCB you will notice that there is a track going from the solder pad, where the black wire is soldered, to R224. Cut the track between the black wire's solder pad and R224. Step 6. Position the 2N3904 transistor under the BNC connector (on the solder side of the PCB) so that the flat side of the case is facing the PCB and the leads are pointing towards P204. Solder the Emitter (lead closest to the edge of the PCB) of the 2N3904 transistor to the end of R224 closest to the edge of the PCB (GND). Step 7. Solder the end of the resistor, which is connected to the base of the 2N3904 transistor, to the end of R224 closest to Q204. Step 8. Solder a wire from the end of R224 closest to Q204 (or to the collector of Q204, as they are connected by a short track) to the blank solder pad on the track located between pin 5 of P204 and R222. Step 9. Solder the Collector of the 2N3904 transistor (remaining leg) to the solder pad where the black wire (on the parts side) is soldered to the PCB. Step 10. Solder one end of the 3.9K resistor to the collector of the 2N3904 transistor (same location as in Step 9) and the other end of the 3.9K resistor to the closest end of R256 (wire link). Before soldering the resistor, cover enough of the resistor with heat shrink tubing so that it will not short with any of the adjacent connections. Step 11. Remove the capacitor from the black wire that goes to the end of the PCB near P203. Install the black wire directly to the PCB. Note: Only the newer NTSC decoders will have the capacitor installed. Step 12. Solder one end of a 3.3K resistor to pin 1 of P203 and the other end to ground. Ground is connected to Pin 3 of P203. After completing the above steps, recheck the modifications to ensure that they have been done properly. Make sure that the track mentioned in step 5 is cut properly. The NTSC decoder is now ready to be used in a JAMMA cabinet. If the picture's colour is not stable or completely absent then the APC control will have to be adjusted. The luminance bias adjustment may also need adjusting, if the APC was not incorrectly adjusted in the first place. PCB adjustments: The Tint, Color, Contrast, and Sharpness adjustments are straight forward to make when using a color adjustment pattern. All laserdisc games have the pattern in their self test options. Do not adjust the APC or Lum(inance) Bias adjustments. If you suspect that one or both require adjustment then follow the following procedure. APC Adjustment: 1. Apply a color bar signal to the Video Input terminal. 2. Turn the Color control fully clockwise and position the Tint control at its mechanical center. 3. Connect a jumper between TP201 and ground. 4. Turn the APC adjustment control until the color bars on the screen are synchronized. 5. Remove the jumper from TP201 and ground. Luminance Bias Adjustment: 1. Connect a oscilloscope to one of the three video outputs. 2. Turn the Lum. Bias adjustment fully counter-clockwise. 3. Slowly turn the Lum Bias adjustment in the clockwise direction until the black level is just at the sync tips. The sync appears fully compressed.