Bally Flip-Flop functioning well. For the most part the game sits inactive but always illuminated ready for play. Power always on whether playing or not. All lights on playfield, in backbox, and on coin door were working fine. Today I was stunned to see that at some point ALL the back box lights and the coin door lights were off. I managed to play a game normally and everything else in the backbox worked normal. Score wheels turned, game played fine. But not one single light anywhere in the back box was lit. Naturally, I figured it had to be the 15 amp fuse for the backbox must have spontaneously blown. I replaced the fuse twice but no change. Still no lights in the backbox nor the coin door. I have done nothing to the machine for nearly a year. It has just been sitting. All Jones plugs secure. Nothing unusual electrically in the house. I have schematics. Any ideas? Thanks! PERPLEXED!

Thanks. I will give all that a go today. Can these things occur with the machine sitting idle?

Went through the steps offered above. Still no backbox nor coin door lights. I've uploaded an image of the fuses block. I did notice the blue wire connectors to the Backcox lights fuse have become blackened. Don't know significance. Any other ideas? Thanks for your help.

FLFOFuseblock2 (resized).jpg

Could that prevent the current from flowing?

Correction, The chared connectors are on the Playfield lights fuse and are functioning normal. The fuse to the right is the Backbox Lights fuse which is not functioning. I clarified in the new image.

FLFOFuseblock2 (resized).jpg

SOLVED. I cut down the two very freyed wires attached to the Backbox Lights fuse at the top of the fuse block and attached them to a new wire connector. Now the all the lights work on Backbox and the coin door. Thanks for your help!