I recently acquired a Bally Hi-Lo Aces. Minor internal cleaning and lubing was completed and game was operating 100% as far as I could tell. Shortly after it was up and running and maybe 10+ games were done I noticed the lights in the cards in the upper playfield were not lighting but the points and lower lights operated as normal. Then the bumper lights stopped lighting. The search began and after checking out some schematics for same vintage other games I determined the switches ( green/yellow and blue) on the number one disk of the score reel were the culprits. So a flurry of cleaning contacts and adjusting was pursued to make the light work but every time the score reel turned the darn lights didn't work again. It was at this point I noticed the score motor wasn't completing its full cycle. These Bally score motors are so awesome that they are hinged at one end so you can stand them up to work and inspect them. So I did and found that the motor would preform its full cycle when elevated. So now I have a 21 mm 1/2 drive socket under one end of a working(for now) score motor.
My question is what do I do now? I also believe a previous operator has this issue as the blue wire switch has some new solder.

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Sorry I just reviewed my post and see that I referred to a 'score reel' that was incorrect it should be 'score motor'

That sounds like a great place to start as I haven't inspected them yet, thank you.
Is there a description anywhere of how a score motor actually works?
It looks like the large magnet moves a disc mounted on a shaft. The shaft enters the grey gearbox and is pulled back after the operation is completed. I have to assume there is a gear being engaged inside the gearbox.
Have these motor assemblies been known to fail over time, or the opposite, made to endure?

I believe I found the culprit. The wire connection on the top of the motor (in plain sight of course) is a spade connector that looked fine on top but was full of crud underneath and was a bit loose. This was also the wire you mention (Normally the SW that keeps the score motor running, in located on the top of stack on the cam nearest the motor) My theory is when I lifted that end of the score motor the spade made enough contact to fully run the motor. I went ahead and thoroughly cleaned and inspected all the switch stacks and hopefully this solves this mystery.
Another example of me ignoring the KISS principle (Keep it simple stupid)
thanks again

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Greetings again, I don't know if I should start another thread to throw up another white flag of surrender but I could use some help.

My Hi-Lo aces has stopped lighting all the specials lights. The specials still count but no lights.

The other thing that I seemed to have made worse is the ball count is working intermittently. I've done my best to adjust the switch on the number 5 disk on the score motor. I put the playfield up and get it counting down but during game play it stops again. The add a ball seems to work fine. On the bright side the game never ends

I haven't found a schematic yet.