EM's are my bag but early System 80's are of interest.

I am way into EM's, They are a challenge to trouble shoot but it’s my era so that’s cool. I always enjoyed the early System 80's from Gottlieb because of my interest in Black Hole. I have one I am putting together from a complete but heavily worn playfield and a better playfield set. I have rebuilt the power supply but have found heavy loads likely coming from the displays so I am checking those over before I proceed further. Time will tell. My EM's span from 1961 Magic Cock, Space Odyssey, Bally Twin Win and a real pain in my butt Big Shot which has a new problem weekly it seems (presently 25 so far). The latest is it thinks ball 1 is 5 and game over upon completion of the 1st ball.