So to start with this machine is a mess. The wiring had been all hacked up but it was playable until recently. The problem was the flippers would stop working while in play. I found a repaired some broken solder joints on the header pins but the problem is still there.

Here's the weirdness. When the flippers are dead the relay is not enabled. By pressing lightly in the middle of the board, hard enough to flex the board, I can turn the relay on and verify the flippers are active.

I have inspected under magnification the relay solder joints, Q15 and the other header pins and they look fine.

Has anybody experienced this?

I stepped through the board pin by pin (in the relay circuit) and didn't find anything that looked broken. I tested continuity and everything toned out. I reflowed some solder where it was questionable.

I tested the transistor in U4 (pins 2 & 3) against other sets and it had the same values.

One thing on the board that I still need to check it the flipper disable at J4-8. The header pins have been replaced but I need to look at the crimp connector as well.

Fixed. After doing all of the above work I knew that if the problem remained it had to be a connector. The only one I hadn't looked at was J3-8.

Pulled the crimp out of the housing and it was crushed flat. Put on a new connector and back in business!