The lights in the backbox of my Bally "Sea Ray" go dark every time both sets of score reels are at zero. This includes all lights: GI, player 1/2, ball number, etc. Both score reels are at zero during and after the reset sequence, of course -- once the ball hits a scoring element on the playfield, the lights come back on. Or, you can manually increment any score reel and the lights come back on. If you go all the way around to zero, the lights go out again.

What on earth could be causing this? I don't even know where to begin looking. I've cleaned two of four jones plugs, and plan to clean the other two, but an issue as predictable as this isn't likely to be a dirty contact.

If anyone has the schematic, that could maybe help... unfortunately the only copy I have cuts off just above all the circuits for the lights.

Thanks for any and all help!

I'll look carefully at the jones plugs, but the backbox ones were the two that I cleaned. We'll see...as for manually moving the score reels:

Any other ideas? Anybody have a schematic (or even a schematic from a Bally of the same vintage)?

Heartbreak! The backglass on mine is in pretty bad shape. I'm planning to make a replacement, after I scare the gremlins out of there.

Not that anybody needed an update four months later, but just in case: it was a dirty jones plug making bad contact. Finally fixed!!

Exactly. Thanks for the help!