The usual causes of a dead System 3 to 7 board set
Most dead boards come down to the same list: failing Scanbe IC sockets, old ROM chips (replace with EPROMs to reduce chips and sockets), a worn 40-pin interboard connector, a dead 5101 RAM at IC19, and failed solenoid or switch matrix PIAs on the driver board. Any PIA not in the state the software expects locks the whole game, even if it only affects one coil.
Systems
Related tips
- Is it the CPU board or the driver board? Boot the CPU alone
- System 3/4 CPU: no clock at the 6800 or MC6875
- System 6/7 CPU: no clock at the 6802/6808
- Identifying a System 3 to 7 CPU board
- What changed on the System 6A CPU board
- System 6 CPU board test points
- System 7 CPU board test points
- Which System 3 to 7 games use which flipper ROM system
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)