The board set passes every Leon test on the bench, but with game ROMs in the game there are no displays, lamps or coils.
Boards pass on the bench with Leon's code but the game is dead
Cause: Blanking is high on the CPU board but does not reach the driver board, almost always because of the 40-pin interconnector. Leon's code only pulses PA2 about twice a second, so blanking cannot be judged with it.
Checks
- With game ROMs fitted, measure blanking at CPU 1J3 pin 4 and at driver interboard pin 37.
Fix
- Replace the 40-pin interconnector.
Systems
Related tips
- Damage after the black and white plugs were swapped
- Slingshot kicker never fires from its switches: loose pin at 2J13
- Freezes mid-game and blows solenoid fuse F2: clean and reseat the 40-pin interconnect
- Replace the 40-pin interboard female connector
- Making new interboard male pins long enough
- Removing the old interboard female connector
- Double-solder the CPU board male header pins
- Replace CPU board power connector 1J2
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)