What was found
ACFT EXPERIENCED A MOMENTARY CABIN FIRE EVENT DURING TAXIOUT TO THE RUNWAY. FIRE EXTINGUISHED AFTER ENGINES WERE SHUTDOWN AND NO FIRE EXTINGUISHER WAS USED. CREW REPORTED PRIOR TO TAKING THE RUNWAY THE F/O EFIS SCREENS FLICKERED AND THEN WENT BLANK FOLLOWED BY THE SOUND OF SEVERAL, 7 CIRCUIT BREAKERS POPPING. PASSENGERS WERE HEARD SHOUTING "FIRE" AND SPARKS/FLAMES WERE MOMENTARILY VISIBLE AT THE CEILING/OVERHEAD BIN AREA AT SEAT ROWS 26-27CDE. MAINTENANCE FOUND WIRE BUNDLES ABOVE SEAT ROW 27CDE SHORTED TO A BRACKET ON THE CEILING PANEL FOR RECEPTACLE R5-3360. WIRE REPAIRS WERE PERFORMED IAW SWPM CHAPTER 20-10 AND THE WDM. ALL SYSTEMS WERE OPERATIONALLY CHECKED AND TESTED IAW THEIR RESPECTIVE ATAS IAW AMM.