What was found
AIR TURN BACK DUE TO THE FA REPORTED A ROTTEN EGG, DIRTY SOCK ODOR. DURING CLIMB OUT, WITH BOTH PACKS ON. AFTER TURNING THE NR 2 PACK OFF, THE ODOR WAS STILL APPARENT AND RETURNED TO DEPARTURE. PERFORMED IDENTIFICATION OF CABIN ODOR IAW AMM 05-50-00-810-831-A, AND TSM 71-00-00-810-802. NO EVIDENCE OF OIL OR SMOKE FOUND. PERFORMED A BORESCOPE INSPECTION TO CHECK FOR WETTING OF THE NR 1 ENGINE IAW TSM 71-00-00-810-802-A, STEPS 1 - 4A (4), NO WETTING NOTED. PERFORMED A BORESCOPE INSPECTION TO CHECK FOR WETTING ON THE NR 2 ENGINE IAW TSM 71-00-00-810-802-A, STEPS 1 - 4A,(4). NO WETTING NOTED.