J1 is the three pins, space, two pins. That's the bottom of the PS. The two pins on the right are Ground. The three on the left are 12V DC input.

Measure J1 harness for 12VDC.

J2 is six pins. All 5VDC output pins. Should be able to measure voltage from ground to any of the pins.

Adjust Res Pot to change voltage.

Measure voltage at MPU. My PS supplies more than 5vdc but by the time it hits the MPU it's around 4.9V

Also one cannot post 80B schematics because of someone owns the bullshit ass copyright

I would NOT over fuse. I could be wrong but I would replace the fuses with the correct amperage and forget about those 32v requirements. 250vac will work.

Here's a great place to source pinball electronics including fuses.
https://www.greatplainselectronics.com/categories.asp

You should run a continuity test on each of the fuses to see if they are good. Pull the fuses out of the holders when you do it.

Also here's a good tech resource:
https://pinwiki.com/wiki/index.php?title=Gottlieb_System_80#/media/File%3AGtb_sys80_1st_gen_boardset.jpg

Alligator clips. Clip one end to your DMM and the other to the lugs. Turn game on. Read measurement. Turn game off, switch lugs.

Radio shack, homedepot, hardware store should have a set of alligator clips.

What is the voltage at the blue/purple capacitor on the MPU. I found in the past, my PS had 5V coming out but by the time it hit the capacitor it was at 4Ish volts. If that's the case play with the trim pot to get more volts.

The game won't boot without 5V at that point in the MPU.

Also, you should buy this:
https://www.pinitech.com/products/gottlieb_piggydeux.php

The piggyduex removes the daughter board card from the system. The daughter board's solder points try out and are a pain in the ass to repair.

Or it works when you turn it on. Lol. System 80b games have gremlins if you don't do all the proper upgrades and mods.