I'm trying to help a friend get his Star Pool up and running, and we've made good progress. But I'm stumped with the current problem and could use an explanation of how Williams machines go from player to player in multiple-player games, or just stay on 1 player in single-player games.

The symptom is: We start a single-player game (one push of the credit button after turning on the machine), the lights on the backglass stay at the "1 player can play" position and the credit unit does stay in the correct position. First ball scores correctly for player one, then when the ball drains, it acts as if a 4-player game is in progress - it correctly (for a 4-player game) goes to player2/ball 1, player 3/ball 1, player 4/ball 1, then player 1/ ball 2, etc. The ball count unit seems to be working correctly...the game just acts as if we're playing a 4-player game all the time. The game ends correctly when all 4 players have finished.

We've cleaned the steppers and they are moving freely. I think the coin unit and player unit are the 2 that would be involved here. There were some issues with the pegs that open/close zero pos. switches on the rotating gear being on the wrong side of the switches - that sort of thing, but I think everything is in the right position now....I think.

We've also cleaned the contacts on all the relays and watched them opening/closing as the armatures move - they seem to be making contact/opening as they should.

I'm more familiar with Gottliebs and how on a single-player game, the player unit gets enough pulses to quickly cycle through all the other players and get back to player 1. I can't tell from the schematic whether this machine is supposed to do that, or does the player unit just stay in one position, or does it get a pulse to reset...? If that's the case, could it be the highlighted switch on the snippet?

Here's a link to the full schematic (it's on IPDB, so I assume there aren't any copyright issues) - hopefully, this link will work:

https://drive.google.com/file/d/1XYR7vcDQkreUccEmQPW7fADcousNJuIi/view?usp=sharing

I've been trying unsuccessfully to figure out how that part of the machine works. If someone has the time and patience to explain how the machine determines which player is active on both single and multiple player games, that would help me pinpoint the problem. I know that will be a bunch of writing for someone, so thank you in advance.

Thanks!
Star Pool player reset relay (resized).JPG

Thanks Dono
The coin unit appears to be working correctly physically - there are 4 possible positions the spider can be in, and if we hit the credit button once, it's in the first position ("1 can play" light is lit on backglass), if I hit the credit button again, the credit unit jumps to the next position ("2 can play" light is lit), the same for 3 and 4 players. I'll have to look at the wiring closely and see if it's not registering 4 players electrically to the player unit somehow.

I assume the player unit should reset at the beginning of a game, what I was wondering is if it should get a signal to reset after the proper number of players have played a ball. Having trouble figuring that out from the schematic.

Thanks for that explanation, HowardR - so if I understand it correctly, the Player Unit does get a pulse to reset after each ball on a 1-player game. That's not what's happening here - instead, a pulse is getting to the Player Unit Step-Up coil, so it's stepping to the next player instead of resetting back to player 1.

If that m/b Player Reset Re. switch at D6 wasn't switching, it seems like that could cause this problem. Am I thinking about that correctly?

Thanks, Howard - it might be a couple days before I can get to the machine, but that m/b switch is the first thing I'll look at - I'll make sure the Player Reset Relay is firing. I'll look at those contacts on the coin unit that you marked as well.

Thanks for the help!

HowardR - thanks for pointing me in the right direction. Took me longer to get back to the machine than I had hoped, but I finally got there today and my buddy and I figured it out.

-Turns out the m/b Player Reset Relay switch highlighted in post #1 wasn't changing because the Player Reset Relay wasn't firing.

-The Player Reset Relay wasn't firing because Ball Count Unit E.O.S. switch wasn't closing.

-The Ball Count Unit E.O.S. switch (attached to the Ball Count Unit S.U. coil) wasn't closing because the Ball Count Unit S.U. wasn't firing.

-The Ball Count Unit S.U. relay wasn't firing because (whew!) one leg of the rotating spider on the Coin Unit in post #4 (the one contacting the red-white wire) was only rarely making contact.

So - many thanks, Howard!