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.