Soon after power-up the controlled lamp bridge rectifier and its trace on the power board get scorching hot and smoke, though the F1 fuse does not blow. With the board repaired, all the CPU-controlled lamps go very dim when the backbox door is closed.
Controlled lamp supply overheats and lamps dim with backbox shut: short at taped splices
Cause: A short in the backbox wiring harness at old splices that had been 'repaired' and wrapped in electrical tape; closing the backbox door pressed the wires together.
Checks
- Test the bridge rectifier out of circuit in diode mode; a bleed resistor on some replacement boards makes in-circuit readings look wrong.
- With F1 removed and the lamp boards unplugged, measure from the lamp supply to ground; then reconnect one connector at a time.
- Open and close the backbox door with the game on and watch the lamps; inspect any taped or spliced wiring near the door hinge.
Fix
- Remake the bad splices properly with solder and heat-shrink, and repair any heat-damaged trace or replace the damaged bridge.
Systems
Games
Source: Pinball Repair help group!! (Facebook group)