Primary finding
Probable cause
Failure (short) of a diode located inside a transformer which is located in the no. 1 generator control unit.
Investigator assessment
Analysis narrative
While awaiting takeoff clearance, the capt stated that he observed a flash of light & smelled smoke. He initiated the pax evacuation checklist & all pax evacuated the acft. Exam of the acft by company maint personnel revealed that the no. 1 generator control unit (gcu) located behind the first officer's seat experienced internal failure. The gcu was removed for further examination. Exam of the unit revealed that a diode located inside a transformer was shorted, which overheated the transformer & produced the smoke. According to boeing, there have been 12 similar occurrences.
Source record
Factual narrative
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