What was found
ENROUTE FROM TOL TO LAX, DURING CRUISE THE NUMBER FOUR ENGINE FIRE WARNING LIGHT ILLUMATED ACCOMPANIED BY THE WARNING BELL. THE FLIGHT CREW FOLLOW COMPANY EMERGENCY PROCEDURES, SECURED THE ENGINE AND DISCHARGED ONE BOTTLE. THE FLIGHT CONTINUED TO LAX FOR AN UNEVENTFUL LANDING.MAINTENANCE INSPECTED THE ENGINE WITH NO EVIDENCE OF A FIRE. MAINTENANCE TESTED THE SYSTEM WHICH REVEALED A DEFECTIVE FIRE WARNING AMPLIFIER AND WAS REPLACED. MAINTENANCE PERFORMED A SUCCESSFUL OPERATIONAL TEST IN ACCORDANCE WITH THE MAINTENANCE MANUAL. THE AIRCRAFT WAS RETURNED TO SERVICE.