Most switch matrix faults show up as row faults

Run the column and row tests first; if they pass, the fault is most likely in the wiring. Note that even a column problem usually appears in the switch test as a row problem.

Systems

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

Related tips

• Which switches are outside the switch matrix
• A single switch does not register
• Check the switch matrix with a logic probe
• Resistor networks in the switch matrix
• Switch row or column error: CPU board or playfield?
• An entire switch row shows closed all the time
• Switch row (return) circuit on the CPU board
• Test the switch row inputs with a diode jumper

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