What was found
SEA- AFTER PUSHBACK, FLIGHT ATTENDANT REPORTED BURNING SMELL IN FRONT OF CABIN, FIRST OFFICER WENT TO CABIN AND CONFIRMED. CONDITION OCCURRED AT IDLE POWER WITH BLEEDS ON. GROUND RAN AIRCRAFT AT IDLE POWER WITH BLEEDS ON NR 1 & NR 2 ENGINE. CYCLED BLEEDS AND HEAT CABIN AND FLIGHT COMPARTMENT. COULD NOT DUPLICATE SMELL. CONSULT WITH CAPTAIN NO BURN SMELL. NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.