SMELL OF SMOKE IN CABIN CAME FROM PAX BAG IN CLOSET. SHORTED OUT COMPUTER BATTERY AGAINST CAR KEYS. FIRE DEPT AND SO AND BAG OWNER OPENED BAG AND ELIMINATED SHORT AND SMELL OF WIRE INSULATION SMOLDERING.

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DURING TAXI OUT FLT ATTENDANT RPTED BURNING SMELL IN CABIN. SO IMMEDIATELY TURNED OFF GALLEY PWR AND CHKED AIR CONDITIONING FOR ABNORMALITIES -- NONE FOUND. SO CHKED ELECTRICAL PWR INDICATIONS -- ALL NORMAL. CAPT TAXIED CLR OF TAXIWAY AND STOPPED ACFT. FO INFORMED GND CTL OF AN UNSPECIFIED PROBLEM. APU WAS RUNNING SO ELECTRICAL LOAD WAS SWITCHED TO APU. FLT ATTENDANT RPTED SMELL SPREADING IN THE CABIN. BOTH AIR CONDITIONING PACKS WERE TURNED OFF. CAPT TOLD FO TO REQUEST FIRE TRUCK. ELECTRICAL SMELL REACHED COCKPIT BUT NO VISIBLE SMOKE WAS OBSERVED ANYWHERE IN THE ACFT. A PAX TOLD FLT ATTENDANT THAT THE SMELL WAS COMING FROM THE CABIN COAT CLOSET. FLT ATTENDANT AND PAX OPENED CLOSET AND FLT ATTENDANT YELLED TOWARD COCKPIT THAT PAX BAG WAS SOURCE. CAPT CALLED GND CTL TO HAVE FIRE CREW COME UP AFT AIRSTAIR. 2 RUNNING ENGS WERE SHUT DOWN TO ACCOMMODATE FIRE DEPT ENTRY TO ACFT AT AFT AIRSTAIRS. FORWARD FLT ATTENDANT PASSED THE AFT FLT ATTENDANT TO DROP AIRSTAIRS. SO WAS ORDERED TO TAKE FIRE EXTINGUISHER TO CLOSET/BAG. PAX/OWNER HAD BAG OUT OF CLOSET. SMOKE WAS SEEN BY SO BUT BAG HAD COMBINATION LOCKS SO SO BROUGHT BAG TO FORWARD ENTRY DOOR TO OPEN BAG OR THROW BAG OUT OF THE ACFT. PAX/OWNER OPENED BAG AND PULLED OUT HOT COMPUTER BATTERY AND CAR KEYS THAT HAD SHORTED THE BATTERY. VARIOUS MELTED INSULATIONS WERE FOUND. SO CONTACTED DISPATCH WITH AN ASSESSMENT OF THE SITUATION AND OUR INTENTIONS. FIRE DEPT PERSONNEL AND CAPT REMOVED CONTENTS FROM BAG AND INSPECTED BAG/CONTENTS. HOT BATTERY AND SOME CABLES WERE REMOVED FROM THE ACFT BY FIREMAN. OPEN FORWARD ENTRY DOOR AND AFT ENTRY DOOR CREATED STRONG WIND THAT AIRED ACFT TO PAX COMFORT AND SATISFACTION. FLT CONTINUED FROM THAT POINT ON ARPT.