As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
10 MINUTES AFTER DEPARTURE, THE PILOT NOTICED A SMELL OF SMOKE. ONE MINUTE LATER THE PILOT SAW A PUFF OF SMOKE FROM THE CB PANEL AND REPORTED IT TO ATC. THE PILOT DIVERTED BACK AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE PERSONNEL WAS DISPATCHED TO THE AIRCRAFT AND DETERMINED THE ORIGIN OF THE SMOKE TO BE A FAULTY AVIONICS MASTER SWITCH. THE SWITCH WAS REPLACED AND TESTED WITH NO OTHER DEFECTS NOTED AND THE AIRCRAFT WAS RETURNED TO SERVICE. (K)