Leon's code with the driver board attached
With the driver board connected the LEDs should still flash together about once a second, and the flipper relay on the driver board usually clicks in time. A silent relay can mean blanking is missing or too short, but System 3 and 4 boards often fail to click it under Leon's code. Blanking can be watched at interboard pin 37 (fourth from the left) with the tester LED.
Systems
Related tips
- CPU locks up as soon as the driver board is connected
- System 6 and System 7 driver boards can be swapped for testing
- Hyperball driver board is unique
- Driver board transistors and what they drive
- Test a 2N4401 pre-driver with a meter
- Add a blanking LED to a driver board
- Spare transistors for driver board and power supply
- Test a TIP120/TIP102 solenoid driver with a meter
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)