Meter transistor tests catch most but not all failures

The diode-mode transistor checks are done with no load, so a transistor can pass on the meter and still fail when it has to carry coil current. Treat a pass as very likely good, not certain.

Systems

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

Related tips

• Lamp and switch matrix transistor positions on the CPU board
• Diode-test readings for TIP36c, 2N4401 and TIP42 transistors
• 50 V coils use PPB TIP36c transistors, pre-driven from the CPU board

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