I have a 1966 Williams Hot Line machine. The basic premise of the game is to roll the ball over a matrix of plastic tabs in the center of the playing field. They are lit up to form the letters, H, O, T, L, I, N, E. Each time you complete a letter pattern a row of lights specific to the letters advances and you’re awarded 300 points. After you complete all of the letters, it knocks for a replay.

My problem is that whenever it advances a letter, it often advances several times, sometimes forever. It happens when those tabs complete a letter, as well as when a roll over lane at the bottom of the field advances it, and when the game is reset.

Looking inside… When I manually just close the advance relay it also happens. In fact when it happens the advance remains closed – otherwise it closes for the 300 points and opens. When I manually run the score motor – it’s used to count that 300 point award – the motor runs its cycle and stops reliably.

Where to look next?

I looked at 1A and 5A and both seem ok. I even pulled the motor service jack - essentially turning off the motor - and pushed it through the cycle by hand. The advance relay turned off without issue.

Also... I see that the big master reset is also activating when it fails - as if it's a new game, not just advancing during a game.

I see on the schematic that a "coin relay" is also a potential path for the advance relay. What is that and where is it? Coin, like money? For what it's worth, this machine has been rigged not to use coins...

Good thoughts. Thank you.

So, where is the coin relay on the machine? And what is the plastic armature?

This machine was modified before I got it to be coin-less. From a previous experience I know it’s missing considerable hardware on its door.

First off, thank you! Thank you everyone for the prompt replies and helpful information. I write software for a living and rely heavily on forums. The response times I've been seeing in this forum is just amazing...

Someone asked to watch the advance relay while its cycling over and over... It is staying energized the whole time.

An interesting clue... While it was cycling over and over, I pulled the motor service jack, stopping the motor. I then loosened the screws on the #5 bank of switches on the motor - hoping to open that 5A switch. And yeah, sure enough the advance relay opened up.

So, I want to conclude that there was nothing else anywhere holding the advance relay energized - just that 5A.

So, is it possible (probable?) that when the motor is running that 5A switch isn't opening enough when its cam comes around? But when I pull that jack and push the wheel around by hand, it opens the advance relay every time...