A 50 V coil, motor or a section of GI controlled by a small relay board under the playfield does not work.

Device switched by an under-playfield relay board does not work

Cause: Cracked or cold solder joints on the relay board are common; the relay or its CPU driver may also be bad.

Checks

• With the game on, clip the relay board "DRV" lead to the side rail: the relay should click and the device should run (or the GI section switch off).

Fix

• Resolder every joint on the relay board.
• If the relay clicks when grounded but not in play, test the CPU driver transistor.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• 50 V coils on early System 11: under-playfield relay boards
• 50 V coil dead on an early System 11 game
• Flashers dead on early games: resistors broken on under-playfield flasher boards
• Whole groups of coils or all flashers dead: A/C select relay stuck
• Controlled solenoids 9-16
• Checking for power at a coil
• What a bad coil diode does
• Center eject dead and solenoid fuse blows at power-up: shorted coil and drive transistor

Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)