I have a Grand Prix which plays mostly as expected, but whenever the 1,000s relay needs to fire (either from a direct 1,000pt score or from scoring enough 100s or 10s to roll over the 1000 digit) it sticks; it happens on all players. It unsticks when I manually actuate the 1,000 score reel on the selected player. The switches by the 1,000 scoring coil seem correct, and when I measure the selected players 1,000 reel coil I don't see any activation voltage across the score reel coil. I'm pretty new to EMs so please excuse some simple debugging I may not have done before asking here. Thanks!

Thanks for the tip. I jumped the scoring coil to the score reel advance coil; it sparked a bit but then freed right up. So jumping the coil then removing the jumper seems to have 'fixed it', I wonder if it was just switch corrosion that cleared up on a jump?

I noticed two other issues: One, the game never needs coins and always seems to start a 4 player game despite only pressing the start button once. Second, one of the chime coils locks on when I turn on the game; its the leftmost coil if you are looking in the coin door.

More contact cleaning on the 1,000 reel switches fixed the stuck chime coil. However the ball advance relay sticks on for the first switch hit of the players ball, and won’t unstick until the ball drains and the next player is up.

Where is the coin unit?