Check the lamp matrix outputs with a logic probe

Steps

• Remove the backglass and power the game in attract mode or the "All" lamps test.
• Unplug CN6 and CN7 at the bottom of the CPU board.
• Power the logic probe from the game and probe CN6 pins 1 to 9 (the row returns; pin 1 is the right-hand pin, facing the board): each should show low pulses.
• Probe CN7 pins 1 to 9 (the column drives): each should pulse.
• A pin that sits steady points to that row or column circuit.

Systems

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

Related tips

• How the CPU-controlled lamp matrix is wired
• Check the switch matrix with a logic probe
• Lamp column still dead after a new TIP42
• Test each lamp column driver with a test lamp
• Test each lamp row driver with a test lamp
• Lamp row still dead after a new TIP122
• A row of lamps stays on solid, works if the plug is pushed sideways: repin the header
• Lamps glow dimly when they should be off

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