Switch matrix damage after working on or cleaning flipper switches on a game with lane change.

Matrix burned by the lane-change switch touching the flipper EOS switch

Cause: On games before Banzai Run (Cyclone and earlier), a low-voltage lane-change switch is stacked on the 50 V flipper EOS switch, separated by a small nylon actuator. If the two touch, 50 V reaches the 5 V switch matrix.

Checks

• Look at the EOS stack: the switch with the diode (left) is the matrix lane-change switch, normally open; the other is the high-voltage EOS switch.
• Check the matrix column transistors and chips as for any coil-voltage short.

Fix

• Turn the game off before adjusting or cleaning EOS or lane-change switches.
• Clean the small lane-change switch only with a business card, never a file.
• Repair the matrix components that were damaged.

Systems

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

Related tips

• Lane change and shooter lane switches don't register: failed column driver Q42
• How the Williams switch matrix is scanned
• Testing the switch matrix with a logic probe
• System 11 switch matrix: connectors and chips
• Switch matrix resistor networks and their values
• Coin door test buttons and special solenoid switches are outside the matrix
• Row or column error: CPU board or playfield?
• Random slam tilts: replace the SRC6 resistor pack on the CPU board

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell