Friend of mine snagged a Gottlieb sys 80b Monte Carlo dirt cheap. He played before purchasing and said all was great. He drove it home, literally three blocks and it was dead except for GI. Every now and the he says it will boot and allow a partial ball and then reset and go blank.
What we've tried: installed a new switching 5v Power supply, did the cabinet grounding mod on the transformer case, and we've re-seated all the board connectors. Also tried disconnecting the reset board. All ROMs and piggy back board are tight.

When the machine is kicked on right now it's constantly beeping and resetting. Display flashes on and off when resetting. Once in awhile you can play a ball, then "beep" game rests over and over again.
Any other ideas??? Thanks!!

Keep in mind I'm about 100 miles from the machine, so I need ideas to check once I journey back.

Thank you, was actually suspecting that little board might be causing issues. Will look into that for sure. I have reflowed solder on many boards.

I Like your device acebathound. Hope it bacomes available