One insert lamp never lights. The bulb works in other sockets, there is continuity to the connector, and a bulb wired straight to the connector lights.
One lamp dead though socket and wiring are good: diode on the lamp board
Cause: The lamp's diode on its small lamp board was bad (or had a cold solder joint).
Checks
- Briefly bypass the lamp's diode on the board; if the lamp lights, the diode or its joints are at fault.
- Look for cracked solder on the diode and socket pads.
Fix
- Replace the diode and resolder its joints.
Systems
Games
Related tips
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- Flash lamp dead on an early System 11 game
- Testing a lamp diode in place
- Testing lamp matrix columns with a test socket
- Testing lamp matrix rows with a test socket
Source: Pinball Repair help group!! (Facebook group)