Hello, I need some help with a LW3 project.

Game has Rottendog MPU004 and original boards for the rest.

Problem: Right Pop bumper locks when activated, either by the switch or in coil test mode. Clarification, the coil does not lock when game is turned on like a typical bad transistor. It locks when you press the start button, or when the switch is hit after game has started. Will note that during coil test mode, it will lock on test and release when the test mode is exited back to attract mode. The switch is not stuck on and tests accordingly and passes physical inspection of gap.

History: game was dead when I got it, and it booted after I recapped the power supply. VUK coil locked when turning on game, replaced tip36 on ppb board to fix that. Here is the strange thing first noticed with right bumper. The coil would heat up ONLY when the game had started, not when in attract mode, not locked either just would get hot quickly and burn. This was true even with new coil, diode etc.
Replaced the corresponding transistor on the rottendog board along with one other that was locking on a flasher.
OK after replacing right pop transistor it no longer heats up during game mode, but it now locks only on activation.
It being a rottendog mpu makes this harder to troubleshoot and Im not sure where else to go.. Ive replaced the pop transistor three times with same results.

Anybody have an idea where I can look next? Im not sure what else controls the special coils on the mpu other than the transistor.
Everything else on the game is working like it should now, but this is the last issue I cant figure out.

Thank you for any help or insight!

OK so Ive never fully understood how to test the PIA chips.. and this is not the original MPU.. its a rottendog. But using your logic... would these PIA in the picture, (U11,U24) be functioning the same as the original 12a 12b or 11c?

and secondly what the best way to test if its truly bad?

Thank you!!

MPU_Rotten (resized).jpg

schem_rotten (resized).jpg

I searched for the dip switch settings, could not find them? Rottendog website appears to be unmaintained and the link to the data east jpg is missing.
I did try flipping them the opposite direction and that certainly changed the order.. I think there is only two settings, Wms or Data east. Nothing specific to a particular game that I'm aware of?

Thanks for the help!

Update.. replaced and socketed u24, and u11. Replaced Transistor at Q2. on the Rottendog mpu
Only change is now is, it locks immediately upon entering the diagnostic menu? As apposed to only in coil test. However, I get same results in game play.. wont lock until its switch is activated.

only the right pop is doing this.. what else is in circuit that could cause this type of behavior? Ive never experienced it before, and it being a Rottendog MPU makes it all the more mysterious..

Thanks for any ideas