Testing a leaf switch diode in place

Steps

• Leave all wires on and the switch open.
• Meter on diode test: black lead on the banded end, red on the unbanded end; expect 0.4 to 0.6.
• Reverse the leads; expect no reading.

Systems

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

Related tips

• Credit button and a whole switch row dead: shorted diode on one switch
• Using the System 11 switch tests
• Cleaning leaf switch contacts
• System 11 switch matrix differences
• Entering the System 11 switch tests
• Strange behaviour across a whole row or column from a switch diode
• Testing the switch columns with a clip lead
• Testing the switch rows with a clip lead

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