Two of the RPM tachometer lamps stay dark even with good bulbs.
Some tachometer (RPM) lamps won't light: failed lamp diodes
Cause: Two failed diodes in those lamps' circuit.
Checks
- Swap in known-good bulbs first.
- Test each lamp's diode with the meter's diode setting (lift one leg to test it properly).
Fix
- Replace the failed diodes; if a pad lifts while soldering, jumper to the next point on the same trace.
Systems
Games
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Source: Pinball Repair help group!! (Facebook group)