What was found
ON TAXI OUT, JUST PRIOR TO TAKEOFF, HAD A BURNING ELEC SMELL WITH VISIBLE SMOKE NEAR A VENT FACING DOOR 4L. INSPECTED APU AIR SUPPLY DUCT, NO LEAKS PTT7046004. INSPECTED AFT GALLEY CHILLERS & FOUND C52 WITH INCORRECT EXHAUST PORT INSTALLATION PTT7046002. ALSO FOUND ONE INSULATION BLANKET LOOSE & BLOWING DUST TO THE VENT. BLANKET CORRECTED PTT7046003. RAN ENGS WITH THE SAME CONFIGURATION AS FLIGHT CREW USED FOR TAXI, NO SIGNS OF SMOKE OR DIFFERENT SMELL. AIR VENT BY DOOR 4L SLIGHTLY WARMER THAN NORMAL, COOLED AFTER CHILLERS SHUT DOWN. BOTH CHILLERS PLACED ON MEL.