Overnight test to separate connector faults from power faults

Steps

• With the game off, pull fuses F2 (solenoids) and F3 (lamp matrix) from the power supply board.
• Switch on and enter the self-test; stay in the first (display digits) test so the digits keep cycling.
• Leave it running for a few hours or overnight.
• If the digits have stopped cycling, the game reset with nothing being played: suspect the interboard connector, Scanbe sockets, board connector solder joints or the 1J2 power connector.
• If it is still cycling, the fault only shows in play: suspect the +5/12 V filter capacitor, a broken coil diode or the switch matrix.

Systems

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

Related tips

• Pressing both flippers resets the game: replace big filter cap C15
• Game resets when both flipper buttons are pressed
• Random lockups from the 12 V logic pin
• Game reboots when the flipper buttons are pressed
• Replace the 3J6 logic power connector
• Burnt GI plugs on the power supply board
• Power circuits in a System 3-7 game
• Cracked header pin joints on the power supply

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