It's possible you've popped part of the video output circuitry on the GX, especially as you mention being highly charged with static whilst all this is going on. Although if you were charged to 50kV and touched the edge connector then it seems a bit unusual it'd take out red & blue but not sync or green (as I'd expect them to all be produced by the same IC).
I do have a Sal2 here but I'll be buggered if I can find it, so I can't have a look at how the video output works on GX - I'm guessing by this stage it's a bit more advanced than just a resistor ladder and is probably output directly from a custom.
The obvious causes are:
1. You did indeed fry something in the video output stage, or worse something more fundamental within the circuit.
2. The JAMMA edge connector has crappy pins that are no longer making proper contact with the board's edge connector (cross your fingers it's this
3. Entirely unrelated to the monitor cleaning, one of those things that just happens.
As to fixing this, we need to get some more detail: first you need to see if you're getting any output on the Red & Blue video output pins. If you google "JAMMA pinout" this will show you the pins of interest. Ideally you'd measure the output using an oscilloscope as that'll directly show you the intensity. You *could* try measuring them with your multimeter - set meter to DC volts, put one probe on JAMMA pin 1 (Ground) and the other probe on either Red or Blue and see what the meter displays with the game running. If you can get the game to show a white cross-hatch grid this would increase your chance of inferring something useful as the colour signals will be stable in relation to each other (not strictly true, but it's a white lie
).
So going with the multi-meter method, take a reading with a probe on GND and one on Blue, then GND and Red and then GND and Green. You're probably going to find that the voltage shown on your meter keeps changing (you're trying to measure a relatively fast AC signal) but the crucial part is whether you see anything between GND/Red & GND/Blue. The voltages will be low because the board may only be outputting 0.75V as a full-intensity. When you take these measurements, make sure the probe is touching the actual plated edge connector on the PCB and not the lugs on the back of the JAMMA harness, just in case the pins are making poor contact.
Once you've done this, if you do get any voltages on Red & Blue, repeat the experiment but touch your probes to the lugs on the back of the JAMMA connector to see whether the JAMMA connector is at fault.
Let us know what you see and then we can figure out the next step.
Good luck!
