What was found
DURING FLIGHT F/A REPORTED STRONG UNUSUAL BURNING SMELL. NOT SURE WHERE IT CAME FROM SUPP A/C. SUPP A/C WAS ON DURING TAXI AND AFTER TAKEOFF FOR 10 MINUTES. AFTER SUPP A/C WAS TURNED OFF, FA REPORTED THE SMELL. AIR TURNBACK TO MSP. GROUND RAN A/C (BOTH MOTORS) AND NO UNUSUAL BURNING SMELL NOTED. SUSPECT SMELL COMING FROM SHELLED OUT A/C GENERATOR. REPLACED AC GENERATOR PN 31342-006, SN OFF 97042, SN ON 99025. REPLACED LT A/C GCU, PN 51634-002, SN OFF 97057, S/N ON 1247.