An extra lamp added for the start button, wired to the Game Over lamp socket, makes the Game Over, Play Again and Ball in Play lamps glow dimly and flicker. Moving its ground elsewhere stops the flicker but the new lamp then stays on all the time.
Added start button lamp makes lamps flicker: tap the non-banded diode side
Cause: The Game Over lamp is a lamp matrix lamp with its own isolation diode. Tying the new lamp to the banded (cathode) side of that diode bypasses it and causes ghosting across the matrix row and column.
Checks
- Look for a diode on the lamp socket you are tapping; on matrix lamps there is one at each socket.
- Note which leg of the socket connects to the diode's banded end.
Fix
- Connect the added lamp's wires across the same points as the original lamp, with the lead that went to the banded side moved to the non-banded side of the diode, so the matrix diode stays in circuit.
Systems
Games
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Source: Pinball Repair help group!! (Facebook group)