Strange problem just started happening with my STTNG. During play the trough will continuously kick balls into the ball launch and then they're launched into play. Three balls are pre loaded in the cannons, so those do not launch, but the trough kickout solenoid will continue to fire repeatedly even after the trough has been emptied. If all balls drain, the trough will kickout another ball before the game has time to recognize that the ball has ended.

I've checked the Trough Optos and they're all functioning correctly. I get one error when I power up the machine "Check Switch 17 Right Ret Lane."

Any ideas of what I should be taking a look at here? Thanks!

Good tip! I'll give it a shot and report back.

I've been trying to diagnose this over the last week or so. Reflowed the solder the ball trough opto board and things seemed to be ok for a few games and then problem presented itself once again. I think the issue lies with the (Trough Up) switch on the opto board. I'll be in the middle of playing a ball and the Trough Up solenoid will fire multiple times, regardless of if there are balls in the trough. It's an inconsistent problem as well which makes it tricky to nail down. When I look at the opto boards with a digital camera, I can see that all 7 LEDs are properly lit.

Do you think it's time to go ahead and replace the ball trough opto boards? Thanks!