Testing coil diodes on the auxiliary power driver board
Steps
- Suspect these if the game resets when many coils fire, as in multiball.
- With the game off, set the meter to diode test.
- Black probe on the banded end, red on the other: expect 0.4 to 0.6 V. Reversed: no reading.
- If the reading is wrong, lift one lead of the diode from the board and test again.
- Replace a failed diode with a 1N4004.
Systems
Related tips
- Testing a coil diode on the driver board
- Testing the diode on a coil
- Why WPC coil diodes are on the driver board
- Testing a coil diode
- Which way a coil diode goes
- Which way a coil diode goes
- Always check the coil diode when a driver transistor has failed
- What the coil diode does and how a bad one shows up
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)