Test a microswitch diode without unsoldering it

Steps

• This assumes standard wiring: green ground wire on the centre lug, diode band on the far lug, plain end and the switch wire on the near lug.
• Pull the push-on green ground wire off the centre lug. If it is soldered, use the fail-safe test instead.
• Meter on diode test, black on the band, red on the other end, and hold the switch closed: about 0.4 to 0.6 V.
• Swap the probes, still holding the switch: no reading.

Systems

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

Related tips

• What a bad switch diode does
• Adjusting a microswitch
• Test the switch column drivers with a diode jumper
• Test the switch row inputs with a diode jumper
• Fit a replacement switch diode the right way round

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