Running a Swemmer MPU; the connectors look to have been recently redone. The score display is fine. Not sure if this is relevant, but the slam switch on the coin door beeps when testing with my meter in diode mode, but the start button and coin slot micro switches do not. Fuses are good, plungers for the coils all move freely. I removed/replaced any non-working bulbs. Power supply reads 5.18 on the 5 volt sections and 11.97 or thereabout on the 12 volt sections.

I haven't done the ground mods since I've seen a few posts saying it isn't exceptionally vital for later 80b machines running Swemmer boards, but it kinda sounds like a wiring/ground issue to me...I've read pinwiki and most other usual linked help sites, but it seems like the step by step troubleshooting goes from how to solve no GI/no displays/no attract to in-game resets so I feel like I'm in between.

I sent a picture of the Swemmer board to the person who makes them and he confirmed all appears well with it as far as wiring and status LED's. I've tried starting a game with 2 and 3 balls in the trough and holding down the switches manually with no response. Red test button near the coin door doesn't do anything/beep in diode mode either.

I keep poking around the machine and nothing seems to be changing, so that might be a good next step--or just do the ground mods anyway to see if it's ground-related.

The slam switch is closed and I don't have the reset board connected since I read that it doesn't seem to be necessary in home use. Also, the PROMS are locked in with the lever, so there isn't much room for them to not fit properly, but I took them out and reinserted them anyway. I attached a picture of my Swemmer MPU. It looks like the 6502 is the chip below the tic tac toe board. I'm not sure which way counts to pin 37, but the second to last pin at the bottom left of that chip measured varying levels between 1.90 and 2.30, but usually closer to 2.20 seemed to be its most common.

Being curious, I measured other legs and some would trigger a reset (with the loud beep), sometimes it would trigger a few solenoids, sometimes a few sounds (like destroy Alpha II or destroy Alpha III), and sometimes it seemed to trigger a game being started with the ball fed into the shooter lane with music being played. I plunged the ball when it did that and only the right flipper kinda worked, but it seemed like the game was more locked up than actually playing.

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"I've tried starting a game with 2 and 3 balls in the trough and holding down the switches manually with no response. Red test button near the coin door doesn't do anything/beep in diode mode either." I've also tried manually activating the coin switches, but those aren't responding.

I don't have a manual, but I have to think it would be quite a rare instance for ball trough switches, coin slot switches, and the start button switch to all be bad. Are those all connected in the same chain of switches? The coin door slam switch is active and being recognized as either being open or closed--at least it seems to be when I open/close it manually.

Tilt and slam switches look to be correct.

The two gray items with stripes (next to the rightmost bridge rectifier) seem to not be stock. They're twist-tied to a lug on the bridge rectifier and both are quite warm after powering on the game for barely a minute or two. The flathead screw that is securing them to the metal plate spins freely, so that seems odd too.

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