I have a 1964 United/Williams Pacer Shuffle Alley I rescued from a barn about a year ago. Got it working, learned a lot about EMs (mad respect for those designers!) and it's been playing well all summer. Recently a problem developed which I can't track down, and I'm hoping someone can point me in the right direction.

The problem flow happens like this:

1. Player gets a spare. The spare light comes on as it should and it advances to the next frame.
2. Next ball is thrown (puck is slid?).
3. Score first increases by 10 (as it should, due to the spare in the queue).
4. Then the score increases by the number of pins that were just hit (as it should).
5. At this point, the player's frame ends and it moves directly to the next frame. This is not how it should behave. The expected behavior is the same player should get their second shot. Everything else is fine. It's really just like the player threw their second shot and missed everything.

Some more observations:

* This happens every time a spare has occurred in the prior frame. It doesn't matter if it's single player or multi-player game. (e.g. in a single player game Ball 1 with a spare in the queue advances to the next frame immediately, in a multi-player game, it advances to the next player immediately.)
* This happens every time a spare is hit, e.g. it's not only on Player 1, for example.
* In a multi-player game, the "spare in the queue" is correctly saved for the proper player. e.g. if Player 1 gets a spare, Player 2 will play correctly, and the problem will not be seen until it's Player 1's turn again, where their next turn ends after they throw only one ball. This suggests to me that the individual player strike-spare step up units are fine.
* In the 10th frame, if the player has a spare in the queue (e.g. they got a spare in the 9th frame), the same incorrect behavior happens, where the first ball of the tenth frame is scored correctly, but it incorrectly "advances" to end the game)
* When this problem happens, after the first ball is thrown (in a frame where the prior frame was a spare), the 1st ball relay trips as expected. However the score motor does a full turn (instead of the expected 1/4 turn to stop at the second ball), and the 2nd ball relays never trip.

So it seems like the question is, in a frame after a strike, why does the score motor make a full turn on the player's next ball in the next frame rather than just a 1/4 turn?

Everything else in the game works perfectly. So if anyone has any ideas of where to look, I'd love to hear them! I've been staring at the schematics for days now, and I feel like I've gone through all the obvious things, so I assume it's something obscure.. some wiper not making contact or something.

Thanks!

Thanks for the response. I will check that, but is there some reason Player 1 strike/spare unit it special? The machine does this regardless of which player is active, so I think the problem is outside of those units.

I'll still check, but it's unlikely that all 6 units have the same problem (I hope!!)