As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING LIGHTING SYS INSPECTION, FOUND PANEL LIGHTS FOR CIRCUIT BREAKERS & SWITCHES INOPERATIVE. TROUBLESHOOTING FOUND A DEFECTIVE DRIVE TRANSISTOR IN DIMMER CIRCUIT. DRIVE TRANSISTOR INSPECTED & TESTED. TRANSISTOR FOUND TO HAVE A BASE TO EMITTER OPEN. FOUND ALL TRANSISTORS TO BE IMPROPERLY MOUNTED ON HEATSINK. INSULATORS PREVENTED DRIVE TRANSISTOR FROM MOUNTING ON HEAT SINK PROPERLY CREATING EXCESSIVE HEAT BUILDUP IN TRANSISTOR. REPAIRED AND CIRCUITS WERE TESTED & HEAT CONDUCTION TO HEAT SINK VERIFIED.