Hi all,
I'm currently tidying up The Simpsons Pinball Party (Stern Whitestar system) and fixing any small problem. When the game arrived, the game would be powered on and it would immediately do a ball search with "5 Balls Missing" on the DMD. I checked all the ball trough switches and they tested ok. I narrowed the problem down to the two opto boards in the ball trough.
After re-flowing solder on the boards, this did not fix my problem. I ended up replacing both boards for longevity.
Now when I turn the machine on, it boots with no errors. Problem solved!
Cheers!
Adam.