What was found
ON FLIGHT 9800 CREW REPORTED ON CRUISE A SLIGHT BURNING SMELL IN COCKPIT. SMELL WAS NOT NOTICED IN CABIN. CREW SELECTED A COOLER TEMP ON LEFT PACK SMELL DISSIPATED. SELECTED WARMER ON LEFT PACK SMELL RETURNED. TURNED LEFT PACK OFF SMELL WENT AWAY. KEPT PACK OFF. AIRCRAFT REMOVED FROM SERVICE. INSPECTED AND FOUND NR 1 PACK DUCT MELTED. REMOVED AND REPLACED DUCT, OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.