Power a System 3 to 7 CPU board on the bench with a PC power supply
Steps
- Use an old AT or ATX computer supply (or a video game switcher). An ATX supply turns on when its green PS-ON wire (normally pin 14 of the motherboard plug) is tied to a black ground wire.
- With a meter, identify ground (usually black), +5 V (red) and +12 V (yellow), then switch off.
- Clip ground to CPU connector 1J2 pin 1 (pins 1-3 are ground).
- Clip +5 V to 1J2 pin 5 (pins 4-6 are +5 V).
- Only if needed, clip +12 V to 1J2 pin 9, the "unregulated +5 V" input, which is really about 12 V.
The PC supply runs from line voltage; keep its case closed.
Systems
Related tips
- How a good System 3 to 7 CPU behaves at power-on
- 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
- System 6 CPU board jumpers J1 to J6
- A System 7 CPU board can run any System 3 to 7 game
- System 3 CPU board ROM layout
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)