Testing a microswitch diode without unsoldering it

Steps

• Confirm the standard wiring: green ground wire on the centre lug, diode band on the far lug, unbanded end and switch wires on the near lug. If the green wire is soldered, use the fail-safe test (cut one diode leg) instead.
• Pull the green wire off its quick-connect.
• Meter on diode test: black on the banded end, red on the unbanded end, switch held closed; expect 0.4 to 0.6.
• Swap the leads with the switch still held; expect no reading.

Systems

• Williams System 9
• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• Testing a diode on a matrix microswitch
• Standard switch and diode wiring
• Wiring a microswitch into the matrix
• Banzai Run and Swords of Fury: lane change is a cabinet microswitch

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell