Hey pinsiders. I'm pulling my hair out on this one.

I've been trying to help my parents out with their Data East Laser War for a while but it has been hard to get back to their house with covid-19 restrictions. I finally had a chance to take a look at it again today.

When we last left off, the machine had a few things it was doing weirdly. A transistor had blown on a pop bumper from a failed diode. I mistakenly replaced the wrong transistor and then did the right one. It then had a weird quirk where it would tilt randomly when other switches were tripped which seemed to indicate a problem with the switch matrix but I could not find anything in particular that would actually be causing that. In the process of troubleshooting that replaced some diodes and like an idiot blew another transistor on a pop bumper.

Good times.

When I returned today I replaced transistor Q8 for the blue pop bumper and when I power on the machine it no longer locks on so that is progress there.

The strange new behavior though is at the machine instantly goes into audits and rapidly scrolls through them as though someone is holding down the button in the coin door to scroll through them. No matter what I do I cannot stop it from scrolling through them and cannot get a game to start.

I have tried unplugging the wires to the coin door in case it is a stuck/bad button but it still does this scrolling behavior with the coin door unplugged. I also tried unplugging connectors on the board in case there is some sort of switch matrix issue but it does it with those unplugged as well.

Does this sound like a board issue then?

The board does not appear to have any battery corrosion on it. A tech they had come out a while back did do a weebley NVRAM mod so they would no longer need batteries.

They bought this game back in 1992 when it presumably came off route after having what looks like a board failure. You can see some scorch marks around the relay on the right hand side of the board and somebody soldered in some wires I'm assuming to replace missing traces. It worked great for a decade or so though so unless something failed after a long time I don't know that that is relevant.

Any ideas on what could cause this behavior?

Doh, that was totally it.

Now is just need to figure out why it displays tilt rest every time a ball goes through the letter R.
Going through the letter A ejects the yellow base or says Danger. This is the problem I was trying to track down last time I was here to no success.

Something is clearly wrong in the switch matrix somewhere but I'll be damned if I can find it.