Many or all coils and flashlamps pull in as soon as the game is switched on.

Nearly every coil energizes at power-on

Cause: The blanking signal from the CPU board is not going high, so the driver board never enables its outputs. It can be a CPU board fault, or a good signal lost in the 40-pin interboard connector.

Checks

• Measure pin 37 of the 40-pin interboard connector (fourth pin from the left): it should rise to at least 4 V almost immediately after power-on.

Fix

• If low at the CPU board, repair the CPU board (dead-CPU section of the guide).
• If high at the CPU but not reaching the driver board, replace the interboard connector.

Pull fuses F2 and F3 before power-on while this is unresolved, or coils will burn.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• All coils or lamps lock on at power-up
• How a coil is switched on
• Coil has power and wiring is good but still dead or locked on
• Spare transistors for driver board and power supply
• Coils 1-8: connector, transistors, PIA pin
• A low resistance coil points to a bad driver transistor
• Coils 9-15 and coin lockout: connector, transistors, PIA pin
• Coil still locked on with good transistors and gate

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)