A single switch never shows in switch test or never scores.
One playfield switch does not register
Cause: Most often a bent or dirty contact, a misadjusted or broken microswitch, a broken wire or solder joint, or a failed switch diode.
Checks
- Look above the playfield for contacts bent together by an airborne ball.
- For a microswitch, check the actuator arm and listen for the click; no click means misadjusted or broken.
- Check the wires are soldered on; with the meter on continuity, check the wire to a neighbouring good switch that shares its column (white) or row (green).
- Meter on continuity: common lug (where the diode band goes) to the normally open lug should beep only when the switch is pressed; to the normally closed lug it should beep only when released.
- Test the switch diode, then check other switches on the same row and column.
Fix
- Clean gold-plated leaf contacts by drawing a business card through them; never file them.
- Repair the wire or replace the switch. If a whole row or column is dead, work back from the switch toward the CPU board.
Systems
Related tips
- A switch does not register in the switch test
- All eight drop targets never register: check the drop target board plugs
- How wiring faults show up in switch test
- Inlane, outlane and drain switches all dead: blown switch transistor Q49
- Strange behaviour across a whole row or column from a switch diode
- Decide whether a phantom switch is in the playfield or the CPU board
- Displays show only 0s and Xs at power-on
- Lane change and shooter lane switches don't register: failed column driver Q42
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell