SDR 96ZZZX4165

Service difficulty report · Power Lampholder · Doug DC931

Difficulty date
July 26, 1996
Submitted
March 26, 2000
Operation
General aviation
Filed by
ZZBR116L
Bruce Aerospace Inc
Make and model
Doug DC931
Part
Power Lampholder
Part number
BR9708001
Condition
Burned
Location
Light System
Component
Bruce · BR9702931NW
Stage of operation
IN
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

MAIN HOUSING HAS A BURN HOLE APPROX 1 INCH BY 0.5 INCH ON RT HAND SIDE WHICH EXPOSED INTERNAL CIRCUITRY. REMAINING MAJORITY OF PLASTIC HOUSING DISTORTED WITH BULGING OF CONTOUR SURFACE IN A FEW LOCATIONS, AND DISCOLORATION FROM OVERHEATING. INDUCTOR AND OVERCURRENT FUSE ARE VISIBLE THROUGH BURN HOLE. FUSE METAL END CAP AND ITS ASSOC AXIAL LEAD HAVE MELTED. THERE ARE 2 DISTINCT FAILURE MODES IN EVIDENCE; CAPACITOR FAILURE AND A SHORT CIRCUIT BETWEEN THE OVERCURRENT FUSE AND INDUCTOR. DEGREE OF FAILURE IS UNPRECEDENTED DUE TO COMBINED FAILURE MODES. WHEN OVERCURRENT FUSE SHORTED TO THE INDUCTOR, IT ALSO SHORTED OUT THERMOSTAT AND THERMAL FUSE LEAVING CIRCUIT UNPROTECTED FROM CAPACITOR FAILING. THERE IS INS

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