I'd like to get an issue fixed, but also learn some new things too.
The issue is that Bally Old Chicago won't advance the ball or player on a multi-player game. It will advance the ball fine on a single player game.
Ball index holds after points are scored
Player up coil tests good (about 10ohms), but does not fire.
It seems that if I manually activate the player up coil my game would work correctly.
Questions:
How and where exactly can I attach clips to manually fire the player up coil?
how can I figure out from the schematic which motor switch I should check?
What is a good way to get at all the score motor switches to inspect and clean them?

Thanks for any advice

Does this mean the motor switches are not involved? Or is that what the 4B in the box indicates? Sorry, another question. How do I access those motor switches to check and clean then?

Hi @rolf_martin_062,
Did you mean the player reset relay? Yes, that one fires after each ball.
I'm learning, a little. In the schematic, the circled 3A SCM indicates the score motor switch changing state, #3 closest to the bottom. I inspected and cleaned that one today, but the same problem persists. Another interesting clue perhaps? If I start a 4-player game and then manually advance the player unit in the back to player 4, and then add some points (so the ball index will activate), and then activate the out hole relay, the player reset relay activates, but they player unit in the backbox does not reset. So, it means that neither of the player unit coils are firing, not the increment or the reset. I will look at that unit closer. I wish I knew how to jumper and fire those coils.