What was found
CRUISE, A LOUD BANG & FLASH OF LIGHT BEHIND F/O SEAT ON ELECTRICAL PANEL, DEBRIS & SMOKE FOLLOWED. NO INDICATIONS OF PROBLEM ON ECAM, STARTED SMOKE REMOVAL PROCEDURES. DISCONNECTED PWR FROM GALLEY, DID NOT DISCONNECT GENERATOR. SMOKE STOPPED 15 MIN. MX IDENTIFIED NR 3 AUDIO CONTROL PANEL AS HAVING BURNT ELECT SMELL; REPLACED NR 3 ACP. LIGHTING CONTROLLER 16LF REPLACED DUE TO HISTORY OF C/B POPPING. OPERATED NR 1 & 2 PACKS, ALL FLT DECK & EXTERIOR LIGHTING, ALL 3 HYD SYS, NO FAULTS FOUND. VENDOR BENCH TEST AND TEARDOWN NR 3 ACP COULD NOT CONFIRM REASON FOR REMOVAL. UNIT HAD BURNT SMELL, NO BURN INSIDE, & UNIT OPS NORM. PIA IC MN3 UPPER BOARD REPLACED, AS Z1 & Z2 OPTOCOUPLERS.