I am trying to bring a Williams / United Omni shuffle alley back from the dead, just like this thread since it's relevant and so I didn't have to start a new one.

I already had to replace both CPU boards and the display driver board with restored ones. Everything worked great for awhile, probably 1000+ games. But now it's not registering the shots on the pins properly.

For example, if you shoot it perfect and it should have been a strike, it's lifting all the pins but not recording a strike (like it missed some). So I have to take another shot to finish the turn. Or if I bowl on the outer edges, sometimes it should just register 2 pins, but all pins lift. Still have to take another shot to finish the turn. Same with other random spots, it seems like more pins are lifting than should be. And sometimes, although less and less frequently, it actually records a strike when it should have been a strike, like it's supposed to.

I've checked to ensure no wires / solder connections in the play field rollover switches broke or came loose, I've checked to make sure the leaf switches have what appears to be the correct gap, that the metal guides are coming down far enough to trigger them, and I've gently brushed all the crud out from between the leafs with a wire brush. Also tried checking for continuity but it seems to only work on some of the switches unless I'm not doing something right.

I have no manual, no schematics, and no idea what I'm doing for the most part. I could also use a fresh backglass & the piece that goes on the pin tray as well.

Just a followup, I ran through the switch test for all play field rollovers and they all register the appropriate switch number according to the switch matrix, including the ones that require 2 switches to be activated for one #.

Also flipped the dip switches & did the CPU test. Put them back to where they were when I was done and now I cannot add credits or start a game and the P6 display flashes while P1-P5 don't.

Phew, what an overwhelming amount of responses! I was starting to think I needed to replace the entire game or scrap it. Luckily my local repair tech is reliable & knowledgable.

Just in case anyone else has similar issues, there is a tiny board in the back of the cabinet next to the sound board that has a row of 10 diodes on it, the board is maybe 3" x 3". 8 of 10 were blown. Why? I don't know. Apparently some of the pin solenoid wiring & some sound wires pass through there to produce the strike, spare & blow sounds so it didn't have to be coded into the game. And with them blown and shorting, it wasn't lifting the pins properly or getting the scoring right. Back up and running now.