Hi Sennap1
do You want "troubleshoot from the very beginning" ?
I found a (hard to read) part of the schematics here: https://pinside.com/pinball/forum/topic/bally-knockout-will-not-start#post-4218165 --- see my JPGs - I have taken from there - we may later discuss the JPGs.
From the very beginning - see here http://www.backglass.org/williams/kordek_archives/introduction_to_bally_flipper_games_blue_cover_100.pdf on page-24 (ori-20) the drawing of the Game-Over-Relay, Interlock-Relay. TWO armatures are mounted - we can actuate "back" - and we can actuate "forth". Toggle off Your Knockout pin, unplug the main power cord (Safety Reasons). Try manually on the Game-Over-Relay this actuate "back", actuate "forth" --- see both states are stable (?) See on page-24 (ori-20) the "Latch-Armature" is hooked-in into an Nylon-Ladder (and switchblades are also hooked-in into the Nylon-Ladder) - the "Trip-Armature" IS NOT HOOKED-IN INTO an Nylon-Ladder.
When You press on the "Latch-Armature" You do "Latch the Game-Over-Relay" --- when You press the "Trip-Armature" You do "Trip the Game-Over-Relay". Do this latching and tripping several times. End with pressing the "Latch-Armature" (latching the relay).
Plug-in the main power cord - WATCH the Game-Over-Relay as You toggle-on the main power switch --- as You toggle-on the main power switch the Relay MUST actuate - it MUST TRIP - does it in Your pin ? Greetings Rolf

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