Test each lamp column driver with a test lamp

Steps

• Remove the backglass, power up and start the "All" lamps test.
• Unplug CN6 (rows) and CN7 (columns) at the lower middle of the CPU board.
• Borrow a 555 socket with a working bulb from the playfield. Clip one socket lead to CN6 pin 1 (the right-hand pin as you face the board).
• Clip a second lead to the other socket lead and fit a 1N4004 diode on its free end, band toward the clip.
• Touch the plain end of the diode to CN7 pin 1, then to each following CN7 pin in turn.
• The bulb should flash on every column pin. No light, or a steady bright light, points to that column's TIP42; test it before replacing. A dark result on every pin may just mean the diode is reversed.

Systems

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

Related tips

• Electronic spares worth keeping for System 11 boards
• Testing lamp-column drivers with a test lamp
• How the CPU-controlled lamp matrix is wired
• Test the switch column drivers with a diode jumper
• Always check the coil diode when a driver transistor has failed
• Lamp and switch matrix transistor positions on the CPU board
• Test a lamp socket diode in place
• Switch row (return) circuit on the CPU board

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