Before I start tearing down the CPU board and isolating components, I wanted to check here to see if anyone had experienced these symptoms or had a theory about the issue.
The Hook I have came to me with several issues, many of which I'm convinced that the previous tech caused. I've been undoing his "work" with good success (He had replaced some PNP transistors with NPN versions). And I backed off the PSU HV drive voltage mods back to factory (which incidentally made me discover the display is actually in great condition when not overdriven).
The remaining issue is that upon starting the game, it thinks some switches have been pressed and goes a bit crazy. The far right pop bumper randomly pops and I get clocks triggered a lot and occasionally "I lost my marbles". The switch test shows no issues, it only seems to be once the game has started and the coils have been energized.
Poking around on CN-10 is interesting. While all pins are around 5v, the far right pin (pin 1 #8) is reading 35-38v when a game is playing, but 5v when it is not. This leads me to believe there's a short somewhere between the coil drive and switch returns, but it's not obvious from the circuit diagram how this is happening.
Does anyone know what's going on?