I have an Eight ball that I just got booting again, turns out there was a mounting issue and the altek board someone had installed was shorting a couple of pins on the switch matrix return to ground. I have no history for the game, other than that several transistors on the solenoid driver board were bad, and a couple of diode on coils on the PF all led to the +43V fuses blowing all the time.
The GOOD: The game boots now, all switches test good in the switch test, all coils (except 1 pop bumper I have disconnected while waiting for more diodes) fire fine in the self test. You can play start and play a game and most everything works.
The BAD: the game likes to randomly award extra balls. Sometimes this happens as the ball drains into the outhole sometimes it happens randomly while the ball is still in play. (This seems to be independent of score, but does seem to happen more frequently on Ball 1. I have seen it happen with scores as low as 4000 and as high as 30000) Additionally, sometimes the game stops making chime noises for some switch hits. This seems to happen especially for the pop bumpers (which still activate the solenoids) and the 500 point stand up behind them. The pop bumpers do occasionally activate the chimes when hit (like they are supposed to). Further, and this just started happening, sometimes the game will drain on ball one or ball 2, and it will simply end the game and not kick out the ball. It does not play the end of game chimes, and the Tilt light does not activate (even though it does work). The ball in play count does not advance, the game just sits there (flippers still active).
So, I'm stumped about what could be causing such bizzare issues. As I alluded to previously, this game has had plenty of issues with shorts, including on the MPU board. Where do I even start looking for these problems??