Switch matrix parts on the CPU board burn out, often with lane change trouble.

Flipper switch shorting into the lane change switch

Cause: The flipper lane change switch shares a stack with the high-power tungsten flipper switch, separated only by fish paper; if they touch, coil voltage runs into the switch matrix.

Checks

• Inspect both cabinet flipper switch stacks and the fish paper insulators between the two switches.

Fix

• Replace worn or torn fish paper and make sure the two switches cannot touch; repair any damage on the CPU board.

Systems

• Bally 6803

Related tips

• Switch matrix connector voltages under the test EPROM
• Switch column 5 dead after swapping in a CPU board
• Why strobe 5 needs its jumper when it has switches
• CPU LED stops just short of the full count
• Some feature lamps out after the backbox was lowered
• What is on the 6803 CPU board
• CPU board test points
• Factory CPU jumpers by game

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)