After an adjustment with the power on, an entire switch column stops working or shows switches from other columns.

Whole switch column dead after working under the playfield

Cause: Coil voltage (32 to 50 V) touched a switch lead. That usually kills one or more 2N3904 column transistors (Q48 to Q55) and can also take out the 74LS244 at 8J, the 4011s at 5J/6J and the PIA at 8H.

Checks

• Use switch edge test to find the affected column.
• Test Q48 to Q55.
• After repair, unplug CN8 and CN10 and enter switch test: no switch should show as closed.

Fix

• Replace the damaged transistors and chips, starting with the 2N3904s.

Turn the game off before adjusting switches under the playfield; a coil lead touching a switch wire destroys the switch matrix circuit.

Systems

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

Related tips

• One switch column dead: parts to check in order
• One switch row dead: parts to check in order
• Switch column (drive) circuit on the CPU board
• Switch matrix dead after an under-playfield adjustment with power on
• Fixing a dead switch column on the CPU board
• Fixing a dead switch row on the CPU board
• System 11 switch matrix: connectors and chips
• Switch row or column error: CPU board or playfield?

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