I'm having a problem with my WCS kicking out additional balls into the shooter lane during play, eventually stacking up several of them. There doesn't seem to be any rhyme or reason as to when they start kicking out. You can play for awhile and then you can feel the coil trying to unjam the balls and then it is eventually ejected into the shooter lane. My first course of action was to test the optos in the trough. I tried that and they all checked out okay. I also tested each opto on the receiver board with a flashlight and did switch tests on all of the optos and they seemed to work fine. I'm aware that a bad diode could also be a possible cause but I'm not sure where to start investigating that. Interestingly, I also get errors every once of a while on switch 16. It will tell me to test that switch which will usually work fine when I test it and the error is cleared. I also notice that the trough stack switch is on the same row of the switch matrix as the #16 switch. Could these be related? Should I replace the diode on the #16 swtich? Other ideas? Thanks for your help.

Thanks for the suggestion. I haven't taken things apart yet, but I will definitely check for that. I'm not very confident that that is the problem, because the balls seem to be sitting okay in the trough, but it sounds like an easy fix.

Awesome idea. I can test this out really easily and it will rule out one thing out as the issue. I will give it a try.

Well, just tried it and no dice. There's a shim in there now and it doesn't seem to have helped. Nothing seems to be getting hung up and the balls are dropping smoothly into the trough. At least that seems to take one thing out of the equation.

As a second thought, my shim might have been too thin. I've had a feeling that something is going on with magnetism and the balls for awhile. I replaced the balls awhile ago and the problem went away. After around 150 games, it started acting up again and it's been getting worse and worse. I'm going to try new balls and see if it goes away again. If so, I'll probably order that part you linked to. I'll also try a thicker plastic shim and see if that helps. I'll let you know how it turns out. Thanks again.

New balls - no improvement. It's starting to kick out more balls almost immediately. Any other ideas?

This problem went away for quite awhile and has reared it's ugly head again. I replaced one of the opto boards and it seemed to help at first and now the problem is back. I put brand new balls in the machine and it's still occuring. It will give several half kicks of the solenoid and eventually kick a ball fully into the shooter lane. Sometimes it stacks up several in there. Any ideas?

I meant to say that I also tried the trough insert sleeve and it actually seemed to make the problem worse.

I checked the diagnostics in the trough opto area and they all seem to be funtioning as they should. All optos showing as closed with five balls in the machine. The trough jam was showing as open. I banged on the playfield a bit and didn't see any switches opening when they shouldn't. I was playing a test game a few minutes ago and I ended up with two balls in the shooter lane and a third trying to eject. The switch 16 issue that I mentioned in the first post is no longer happening.

Bump for ideas on what to try next.

Okay, here's what I've tried recently. I reflowed the solder on the 7-opto switch board that the opto boards are connected to. The problem is not worse, not better. Today I tested all of the diodes on the row and column of the ball jam opto. It really seems to be related to that somehow because of the way the solenoid "half-fires" and seems to be trying to unjam the ball. The diodes all checked out okay. I'm really stuck on what to try next. I've heard that the chips on that board sometimes go bad. Could this cause the problem I am seeing? Should I replace the whole board? As an FYI, the problem was really bad (continous balls into the trough) and I unplugged the power to that board and plugged it back in. I was then able to play two games successfully. Not sure if it is related or not. Any ideas on what to try? I'm totally stumped at this point and am considering calling someone in, so any last ditch ideas you have would be really appreicated.

Just to follow up, the issue is fixed. It was a bad connection on the receiving ball jam opto. After reflowing, the problem is gone.