Yellow instead of red on Mechanized Atttack

CodeWhite

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Hey guys,

Im in a little need of help so I can get this project done and move on. About a year ago I bought a Mechanized Attack machine. When I fired it up, I noticed that the color red was not being displayed on the monitor. I tracked the problem to the PCB connector, and found that if I wiggled it around the red would appear and everything looked great. This led me to belive that one of the wires going to the connector was loose.

After fixing this problem, I restored the cabinet which was in rough shape. I also completed a cap kit on the monitor for prevenative maintenance. I put everything back together, fired up the game, and found that there is a new problem. The problem is that everything that is supposed to be red in the game is now being displayed as yellow. All the other colors are fine. I tried messing around with the PCB connector again but it doesn't fix the problem. Now it is my understanding that red and green are mixed to make yellow which would mean that its not a monitor issue since the red gun is working. So my question to the arcade gurus is where should I start? Should I pull apart the PCB connector and look for a short? or should I be looking somewhere on the PCB itself for the problem?

Any help or direction would be appreciated. If pictures are needed I can post a few once I get home from work.

Thanks in advance.
 
You could have a short between red and green in the wiring. But that would also mean that anything that was supposed to be green would also be yellow. Couple of places to check - make sure the wiring isn't shorted anywhere, and make sure that the metal tabs (if present) on the neckboard transistors aren't touching each other.

What kind of monitor is this?

-Ian
 
Ian,

Thanks for the reply. I want to say that it is a wells garder k7000, but I will have to wait until I get home to confirm.
 
Now it is my understanding that red and green are mixed to make yellow which would mean that its not a monitor issue since the red gun is working.

Good logic, but not necessarily true. I have a tube now that is heavily biased blue. No gun shorts that I can find, but to color properly it needs red and green maxed and blue at minimum. Checking voltages at the neck, it's not that the blue drive circuit is presenting a "hot" signal, or that red and green signals are weak. For whatever reason any input to the blue gun is amplified, and normal inputs to all three results in a heavy blue bias. All that said, my problem doesn't sound like your problem. Just making the point that because you have a color present doesn't mean that gun isn't malfunctioning.

I would start with the monitor first because it's easy to test. Disconnect and/or swap each color input one at a time and see what happens to a test picture. If you drop red (or green) and still have yellow, it's in the monitor. If not, it's in the harness or video board.

If it's in the monitor, get a schematic and repeat that process at the neckboard inputs from the chassis. If you drop red (or green) and still have yellow, it's in the neckboard or tube. If not, it's in the chassis.

If it's in the neckboard or tube, repeat that process of dropping and swapping colors at the tube inputs. If you drop red (or green) and still have yellow, it's in the tube. If not, it's in the neckboard.

HTH
 
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