Closing one switch triggers an unrelated event, such as an inlane firing a slingshot or a ramp shot causing a slam tilt.

One switch fires something unrelated (phantom closures)

Cause: A shorted switch, from an airborne ball pushing contacts together or a failed switch diode, confusing the matrix.

Checks

• With the glass off, start a game and close switches by hand until you find the one that causes the phantom event.
• Look up its number in the manual. The short is probably one of the four switches at the corners of its row/column square: for switch 53 (column 7, row 5) check 53, 39 (column 5, row 7), 37 (column 5, row 5) and 55 (column 7, row 7).

Fix

• Repair the shorted contacts or replace the bad diode on the switch found.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Phantom drain on every left ramp shot: two wires fused inside heat-shrink

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Three, Clay Harrell (pinrepair.com)