Fit coil diodes with the band on the power lug
The band goes to the power lug, which has the heavier red or purple supply wire, usually two wires because power daisy-chains between coils. A diode fitted backwards shorts and is ruined the moment power is applied. Copy the old diode's direction only if you are sure it was right; check the schematic when in doubt.
Systems
Related tips
- Testing coil diodes on the auxiliary power driver board
- Checking for power at a coil
- Where the coil diodes are on System 11
- Firing a coil by grounding its ground lug
- Coil-mounted diodes: replace rather than test
- Testing the diode on a coil
- System 11 coil outputs
- 50 V coils on earlier System 11 games
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)