What was found
AIRCRAFT TT: 122.6 HOURS. CREW IN-FLIGHT HAD YAW DAMPER, BOTH HSI FLAGS AND THEN NOTED BOTH INVERTERS FALLING OFF. CERTIFICATED REPAIR STATION DISCOVERED THE TAIL BEACON LAMP FILAMENT AT THE BASE OF THE LAMP SHORTING IT OUT. THIS MIGHT BE SETTING UP SOME KIND OF RADIO SIGNAL GETTING INTO THE INVERTERS KNOCKING THEM OFF-LINE. TURNING THE BEACON POWER OFF, THE PROBLEM WILL GO AWAY. SUBMITTER STATED THIS IS THE SECOND AIRCRAFT SEEN WITH THIS PROBLEM.