What was found
BOTH COMM`S FAILED DURING FLIGHT. ACFT RETURNED TO DEPARTURE. PRIOR TO THE AVIONICS POWER BEING TURNED OFF, THE AVIONICS TECHS DUPLICATED THE DISCREPANCY. CYCLED CIRCUIT BREAKERS 1 AT A TIME FOR EACH OF THE GARMIN GTN-750`S, NAV/COM/GPS/MFD, WITH NO CHANGE. CYCLED THE CIRCUIT BREAKERS FOR THE GMA-350 AUDIO PANEL. AFTER THE GMA-350 AUDIO PANEL RESET THE DISCREPANCY WENT AWAY. THE PILOT REPORTED THIS HAD HAPPENED ONCE OR TWICE BEFORE. PERFORMED OPS CHECKS OF THE GTN-750`S AND THE GMA-350 AUDIO PANEL IAW GARMIN INSTALLATION MANUALS. NO FAULTS WERE FOUND.