Good Morning, here is an interesting issue!
I was not going to post till I replaced the caps on the sound board and switches (kits due Thursday) but after poking around last night thought I'd get the ball rolling.
Bally Star Trek- Works fine but the slingshots at the bottom have no sound effects or weak sound effects and sometimes garbled/wrong sound effects.
Pins on MPU, lamp driver board, solenoid board have all been reflowed, ground mods done to solenoid board and it has a new main cap, the sound board has a new main cap and the bridge rectifier board is brand new.
Tried different sound dip switch settings with no change. Now here is the interesting part.
I have sling shot sound effects if I disconnect the slingshot coils or even hold the coils manually with my finger so they can't move in the fully open or fully closed position. The sound effect only goes away when the coils are allowed to move full stroke. Its hard, it doesn't go away totally but you can still hear it faintly. I have looked close at the switches to make sure nothing is being grounded out and everything looks fine.
The MPU is clearly seeing the switches as the slings are firing and there is a "call" for the sound effect, what would cause the sound to drop out or lose 90% of its volume which the coil actuator goes full stroke? Not an issue with any other switch or the pop bumpers.