First off, CONGRATULATIONS! You just acquired my favorite game of all time! It’s punishing, but sooooooooooooooo worth it!

A couple things:
1. Probably needs a fuse update (or protection) on the bridge rectifiers.
The game can start your wiring harness on fire if a rectifier fails on.
2. Pull every board and examine all the pins for the plugs on the back side of the boards. Look very closely, and see if there are hairline cracks. Reflow those pins.
3. Yes, DO check the 40 pin connection between the MPU and driver board. They should probably be replaced.
4. Look for any burn at a plug, both on the boards, and the harness plugs in the “neck” of the game, between head and cabinet (body). If so, purchase a molecule crimping tool and molecular trifurcon connectors. I like to get mine from Jameco or Great Plains Electronics.
5. Look at the power supply, and see if any fuses have burn, or are blown.
6. Put the game in test mode, the button switches inside the coin door. This will help with switch errors.
7. Look at the MPU. Any battery corrosion? If so, ship that board out for service. If chips are socketed, push and wiggle them a little.
8. Look over the wiring under the playfield, and see if anything is loose or broken. Putting game in test mode will help isolate any errors.

After that, check in here again.