Williams CPU boards only self-test when asked
Unlike Bally boards of the same years, these CPU boards do not run a full self-test at power-on; the real test only runs when the diagnostic button on the CPU board is pressed. Results show on the two CPU board LEDs (and the 7-segment LED on System 7).
Systems
Related tips
- Chips a System 7 CPU board needs to run the Williams test ROM
- Replacing the 6802 CPU with a 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
- System 6 CPU board jumpers J1 to J6
- A System 7 CPU board can run any System 3 to 7 game
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)