What was found
AIRCRAFT WAS GROUNDED: UNIDENTIFIED ODOR EMANATING IN THE LAST 3 ROWS OF MAIN CABIN. THE ODOR IS COMPARABLE TO A BURNING PLASTIC SMELL AND HAS STRONG CHEMICAL LIKE PROPERTIES. ODOR WAS NOT CONTINUOUS AND SEEMED TO COME AND GO IN WAVES. ODOR WAS DETECTABLE BY MULTIPLE PASSENGERS AND AFT FLIGHT ATTENDANTS. FOUND FAULTED POWER SUPPLY AT SEAT 28ABC. REPLACED 28ABC (ISPS)-IN-SEAT POWER SUPPLY. RAN PACKS WITH APU FOR OPS CHECK, NO ODORS NOTED. PER AMM 23-81-05.