How many flashes on the MPU when powering up?

Is there a glow in the score displays?

Since there are no flashes on the MPU, it's time to check the power supply voltages. List what the voltages are for each test point on the rectifier board and the Solenoid Driver Board (SDB) and report back.

Those are unusually low voltages for the SDB. What readings do you get on the rectifier board? One of the test points is AC voltage, I don't remember which one. Refer to the Pinwiki guides for the voltages. Also, as Astill pointed out, how do the connectors look on the rectifier board? Are they burned, melted, etc?

I think you can move it if MH is working, but if there’s something downstream that’s bad, you might blow that board, too.

If you’re in over your he’d like you suggest, wait until your buddy comes over and begin systematically troubleshooting per the PinWiki Bally/Stern guide. It will walk you through checking the power supply first, then connecting the other boards one at a time to find issues. There’s no point in shotgunning an issue when there exists an established logical progression of troubleshooting and bulletproofing.

I think the transformer and rectifier board are one complete module. That means a few screws and connectors are involved- no soldering.

Ok. To me, those moves pretty well confirm your problems are with the connectors/wiring assemblies. Look closely at the connectors - are the pins green looking or really tarnished badly? Remove one of the pins and look at it. Does it look worn? Chances are one pin would be representative of the others.

Try checking resistance between the pins, following the wiring diagrams. I think you’ll find they read bad.