Hello everyone. I'm kinda new to Sterns, as I just got my first Stern (a TSPP) within the last year. It's worked great up until about a month ago, when it randomly started kicking an extra ball into play during an active ball for no reason. Based on my Williams/Bally experience, I checked all the switches in the ball trough, cleaned the optos in the trough, and checked the shooter lane switch. I put the machine in switch test mode, and rolled balls down the trough and all switches seemed to register fine, although I suppose there could be an intermittent switch or opto issue causing this.

I thought I had it fixed with the testing and cleaning mentioned above, because it played fine for a while, but yesterday during single ball play, it kicked a ball into the shooter lane. Then another. Then another. And finally it kicked the last ball into the shooter lane. So I'm playing, having a great game, and there a 4 balls sitting there in the shooter lane. I had an Itchy and Scratchy multiball ready to go, so I figured maybe if I activate that mode it would clear this issue, which it did. I started the Itchy and Scratchy multiball, and the auto plunger had enough beans to kick all 4 balls out onto the playfield at the same time. I then played through the multiball, and all balls drained but 1, and I finished the rest of the game with no further issues.

Has anyone else have this problem with a TSPP or another Stern with the same style of ball trough? Maybe all Stern ball troughs are the same, I don't know. I'd love to know exactly where to look to remedy this issue.

Thanks in advance for any info.

Jeff R.

I should add that I made sure I only had 5 balls loaded in the game too, LOL. I know from my W/B machines that having an extra ball in the machine can lead to weird ball kickout issues.

Cool, thanks for the suggestion! I'll do a little extra investigation on the last trough switch!

Alright, I think I got it. I figured I'd post results for anyone else that may have this issue in the future. Once again I took all the balls out of the trough, and had the playfield lifted on the service rails with the machine in switch test mode. I was testing the trough switches and at one point I turned my back on the machine and I heard a switch open and close a few times by itself. I wheeled around and looked at the DMD and it said the last switch activated was the ball trough jam opto. I previously checked and cleaned the ball trough opto boards, and I didn't see any cracked solder joints or anything odd, so I just said screw it and replaced the opto boards with new ones from Pinball Life, which cost less than 20 bucks.

After swapping in new ball trough opto boards, everything seems fine after several games (knock on wood). In fact, I just had my best and longest game ever on the machine, with no problems.