What was found
AIR TURNBACK, FLT CREW REPORTED STRONG ODOR OF SMOKE IN CABIN, CONCENTRATED AT ROWS 17DEF & 18DEF. ODOR STRONGER AT EYE LEVEL AND STRONGEST AT WINDOW SEAT. NO SMOKE VISIBLE AT ANY TIME. INSPECTED AIRCRAFT, NO DEFECTS NOTED. COULD NOT DUPLICATE. INSPECTED E&E COMPARTMENT, NO DEFECTS OR ODORS NOTED. INSPECTED BEHIND PSU'S AT ROWS 16DEF THRU 19DEF. NO DEFECTS OR ODORS NOTED. PERFORMED TASK 24-00-00-810, NO FAULTS OR DEFECTS DETECTED. RAN NR 1 AND NR 2 ENGINES AND NR 1 AND NR 2 PACKS, NO DEFECTS OR ODORS NOTED. INSPECTED SEB'S, VOU'S AND SEAT TO SEAT CABLES FROM 15DEF TO 20DEF. NO ODOR NOTED. INSPECTED ALL CONNECTIONS, NO DISCOLORATION OF CONTACTS. ALL CONNECTORS SECURE.