I've been having a short problem on my Congo for a little while. Short also happens when just playing the game. A whole column of switches go out (all the AMY lane switches and CONGO targets in lower playfield). Pressing any of those switches in the test menu reports a row short across the row of that switch. If I replace the U20 chip, everything will be fine for a few days and then same problem without doing anything to the game. I've done a lot of work to the game in the past but this started happening after most of the work.

I get that there is a short somewhere with metal touching metal. I've tried to following the wires from the switches that go out but cannot find any bare wires or anything suspect. I also just looked over all the wiring trying to find any issues. I found a few things that could of been soldered better but fixing those did not help. Nothing looks hacked or burnt. Where should I look for the short? Would it be something with the wires relating to the switches that go out or could it be somewhere else? I'm still a novice at repairs so not really sure how to address a problem like this.

Anyone have switch shorts happen during gameplay?

Thanks for the info. Didn't think about the short being internal to a switch. Could that be any switch or just one on the column of dead switches? I know these can be tough to figure out but hoping to get at least some direction.

Can a pop bumper bulb cause this problem? I have one that is finicky - sometimes goes out and then back on. I thought it was just a contact issue with the bulb but maybe bigger problem? Seems like the gi is on a different circuit than switches but that's the sort of thing I don't know.

Just to follow up, I think I fixed the short. It's been playing short free for a while so looking good. It looks like the problem was the main bundle of wires that go from the play field to the head. It was resting in front of the speaker and was catching on to the speaker grill or other metal speaker bits when the play field was pushed back into place. I found one thin wire that looked like it had some insulation wear. After fixing the wire, moving the wires behind the speaker, and replacing the U20 chip everything has been good for many games.