What was found
(CAN) PILOT REPORTED ELECTRICAL FIRE SMOKE DETECTED WITH TRANSPONDER INOPERATIVE AND ELECTRICAL FIRE SMOKE DETECTED WHEN TRANSMITTING ON COMM 1. FURTHER DISCUSSION WITH PILOT DETERMINED THAT NO ACTUAL SMOKE WAS SEEN AND ONLY AN ELECTRICAL BURN ODOUR WAS DETECTED. TROBLESHOOTING FOUND OTHER AVIONIC SYSTEMS FAILING UNTIL ELECTRICAL BURNING ODOUR WAS ISOLATED TO THE AVIONICS MASTER SWITCH. AVIONICS MASTER SWITCH REPLACED WITH NEW PART, WITH NO FURTHER ODOR DETECTED.