So we found and brought a Space Shuttle back from the dead. Got a mainboard from a doner Sorcerer (RIP) and changed the jumpers, swapped chips, recapped the power supply, ebayed a display driver, and fixed a dozen switch and light problems. Passes all tests and plays fabulously now. Problem is that mostly every game we eventually get intermittent scrambled sound effects triggered by playfield switches and crazy tones that generally culminate in complete sound shutdown requiring a power cycle to restore any sound (Pop bumpers and slingshots seem to lead the way triggering odd tones, but sometimes it will start to scramble right at initial ball launch) The lights, displays, and gameplay are completely unaffected. We have checked all of our connections, done countless continuity checks, and purchased and replaced both the main and sound EPROMs on the main board thinking we might have had a flaky EPROM. We have jumper bypassed and even replaced the speech board completely during testing and the same problem still occurs, so I think it's safe to assume that it's not the problem. Any help appreciated. I learned long ago that dreaded intermittent faults often repeat and become tribal knowledge to a few folks, I'm hoping someone has seen (or more accurately heard) this one before. My Next guess is to recap the main board. Thanks!

Thunder Hill