At power-on the displays flash briefly at high brightness, the speakers are noisy, and the game goes no further.
Displays flash bright and speakers noisy, game does nothing
Cause: A blanking circuit fault. Blanking shuts off displays, coils and lamps when the CPU is not running; here the 555 timer at U43 and the 2N4403 at Q50 had both failed.
Checks
- With a logic probe, probe U20 pin 2 or U43 pin 3 while switching on: expect a few seconds low, then steady high once booted.
Fix
- Replace U43 (555) and Q50 (2N4403).
Systems
Related tips
- Blanking LED wrong, or all solenoids pulse and blow a fuse at power-on
- Solenoid fuse F2 blows at power-up as every coil fires: CPU blanking circuit
- Blanking stays low: timer, C31 and Q5
- MPU LED locked on with no flicker: likely causes
- MPU boots only some of the time
- Five flashes only: U12 timer or open R113
- Fliptronics flipper coil wired wrongly
- STNG: under-playfield diverter coils lock on during play
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell