How a good System 3 to 7 CPU behaves at power-on
With game code: a good System 3-6 board flashes both LEDs briefly and turns them off; one or both staying on means a lockup. A good System 7 board shows "0" briefly, then goes dark and stays dark; a "0" from the instant of power-on with no flicker is a lockup. A running board also holds blanking high (about 4 V), measured at interboard pin 37 or at pin 4 of CPU connector 1J3. With Leon's EPROM running, the System 3-6 LEDs flash together about once a second and the System 7 display flashes "0" every second.
Systems
Related tips
- Power a System 3 to 7 CPU board on the bench with a PC power supply
- 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
- Run a System 6/7 CPU board on +5 V only
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)