At power-on many coils and/or lamps energise at once.
All coils or lamps lock on at power-up
Cause: The blanking line is broken between the boards, usually by a worn 40-pin interconnector, so the driver gates see a floating input. A CPU that does not run leaves the PIAs as inputs, which adds to it.
Checks
- Pull F2 and F3 at once to protect coils and lamps.
- Compare blanking at CPU 1J3 pin 4 and driver interboard pin 37.
Fix
- Replace the 40-pin interconnector.
- Repair the CPU fault if the board is not running.
Locked-on coils overheat quickly; switch off at once.
Systems
Related tips
- One or a few coils lock on at power-up
- Nearly every coil energizes at power-on
- Coil locks on and new transistors don't help: a failed 7408 on the driver board
- How a coil is switched on
- Coil has power and wiring is good but still dead or locked on
- Slings and pops all burned at once: CPU lock-up from the 40-pin interconnect
- Solenoid fuse blows at power-on and solenoids fire: driver board logic chips
- Replace burnt 3 watt lamp resistors with 5 watt
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)