Quoted from Quinnball:Disclaimer: I am brand new to pinball repairs. So I bought a Gottlieb System 1 torch machine today and It turns on, shows me 0's on all the displays but the high score display is busted for sure. shows broken numbers and letters, the game wont start and the diagnostic button on the coin door doesn't seem to be doing anything too. there was some battery damage on the CPU so I cleaned and replaced it. The lady I bought it from said it was working until she moved it a few days back. also checked the slam tilt switch as well. any suggestions what I should try next?
Do you have schematics? Are you handy? Experience repairing electronics?
Check out the Pinwiki page for System 1 games. It's going to be very helpful.
https://www.pinwiki.com/wiki/index.php/Gottlieb_System_1
There's a section on how you can diagnose your display issues, as well as where to start with a non-booting MPU.
https://www.pinwiki.com/wiki/index.php/Gottlieb_System_1#MPU_Boot_Issues