What was found
SEA - FLT 27 - DURING CRUISE A LOUD BUSS HEAD OVER COCKPIT SPEAKER AND WAS SILENCED BY PUSHING THE PA SELECTOR. NR 1 FLT ATTENDANT REPORTED SMOKE FROM THE VIDEO SYSTEM. 1ST OFFICER INVESTIGATED AND DISHARGED THE HALON FIRE EXTINGUISHER INTO THE AREA. C/B'S WERE PULLED WITH NO FURTHER SMOKE. A/C AIR INTERRUPTED AND RETURNED TO SEA WITHOUT FURTHER INCIDENT. THE SYSTEM WAS DEACTIVATED AND THE VIDEO SYSTEM CONTROL UNIT WAS SENT TO THE SUPPLIER. TECHS FOUND THE UNIT HAD A LOW RESISTANCE FAULT FROM DC GROUND THE VIDEO 3 HI SIGNAL. THIS PATH PROVIDED THE ENERGY AND VOLTAGE NECESSARY TO CAUSE SMOKE TO APPEAR IN THE CABIN. THIS FAILURE IS AN ISOLATED INCIDENT. (M)