Use the tester LED, not a logic probe, for driver board tests
Logic probes pick up noise and can mislead on these driver board checks; a tester LED clearly blinks once a second with Leon's code. Testing transistors and chips unpowered with a meter is often quicker still.
Systems
Related tips
- Add a blanking LED to a driver board
- System 6 and System 7 driver boards can be swapped for testing
- Hyperball driver board is unique
- Driver board transistors and what they drive
- Solenoid fuse blows at power-on and solenoids fire: driver board logic chips
- Test a 2N4401 pre-driver with a meter
- Leon's code with the driver board attached
- Spare transistors for driver board and power supply
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)