MPU had some battery corrosion. I repaired and MPU is now booting into attract mode, but the test button on the door doesn't do anything. Also, cannot start a game because coins don't add credits. The service credit button doesn't do anything either. Seems like everything on the coin door is dead (except the slam switch on the door works). Any suggestions or tests/measurements to help me fix this problem?

The battery did not appear to damage J205. I have checked the ground wire at pin 10 (pin 11 is an error on the schematic). Have verified the black wire and pin each measure ground. Also checked back to the coin door switch assembly. The black wire is intact and measures continuity to ground.

I traced each pin at J205 back to the diodes and there are no broken traces. I also checked diodes D11-D18 and found D15 shorted, which I replaced.

Is there a way to check U16 and U17? I have a DMM and Logic Probe, but not sure how to verify if these LM339's are working. Or is this the logical next place to check? Thank you for your guidance.

I'm always a little afraid to do board work, and I see the traces on this board are VERY tiny. The parts after shipping are about $4-$5 each. Don't want to replace good parts with good parts if I can help it.

Before I begin wholesale replacing parts, isn't it possible to check some voltages, resistances, enable signals, etc. to pinpoint the problem?

Thank you for the test procedure. Exactly what I was looking for. I'll work on it tomorrow when I am fresh and can concentrate. I'll report back the results.

FIXED! Thanks again Chris for guiding me to a solution.

The procedure led me to find a missing 12V supply to U16. Repaired that and all is working 100%.