What was found
EWR---CO3384, CREW REPORTED, NOTICED ELECTRICAL BURNING SMELL IN AFT CABIN AREA, COULD NOT ISOLATE. TURNED OFF ALL CABIN LIGHTS, STILL SMELLED. TURNED OFF RECIRCULATION FANS NR 1 AND 2, STILL SMELLED. MAINTENANCE TROUBLESHOT AIRCRAFT, FOUND BURNT LIGHT SOCKET IN SEAT ROW 7A/B OF SIDEWALL LIGHTS. INSTALLED NEW SOCKET. OPS CHECKED GOOD OF SIDEWALL LIGHTS IAW ATR42 MM 33-20-00. AIRCRAFT RETURNED TO SERVICE.