Testing a coil, switch or flipper diode with a meter

Steps

• Switch the game off.
• Unsolder or cut one lead of the diode from its lug.
• Set the meter to diode test. Black lead on the banded end, red lead on the other end: expect 0.4 to 0.6.
• Swap the leads: expect no reading.
• If either reading is wrong, fit a new 1N4004 (band to the power lug).

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Which way a coil diode goes
• Which way a coil diode goes
• Test a 1N400x diode on a coil, lamp socket or switch
• Testing the diodes on a flipper coil
• Testing the diode on a coil
• Spare diodes for coils and switches
• A cracked coil diode keeps killing its driver transistor
• Resets from damaged flipper coil diodes

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)