As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT THE FLIGHT CREW NOTICED LIGHT SMOKE COMING FROM THE ATC TRANSPONDER PANEL IN THE COCKPIT. SWITCHED PANEL TO STBY AND THE SMOKE IMMEDIATELY STOPPED. OPENED BOTH TRANSPONDER CIRCUIT BREAKERS. THE FLIGHT CONTINUED TO DESTINATION. MAINTENANCE REPLACED THE ATC PANEL IAW AMM 34-53-03. OPERATION CHECK NORMAL, ACFT RETURNED TO SERVICE.