What was found
IN CRUISE AT FL 390, LOWER FWD CARGO FIRE WARNING (BELL/LIGHTS) CAME ON. WHEN FIRE BOTTLE NR 1 WAS DISCHARGED, FIRE WARNING LIGHTS WENT OUT IMMEDIATELY. FM VOL, 1 PAGE 2.12.2 PROCEDURE WAS ACCOMPLISHED SUSPECTED FAULTY WARNING SYSTEM. F/E MADE PHYSICAL INSPECTION OF CARGO COMPARTMENT IN FLIGHT AND FOUND NO EVEIDENCE OF HEAT, FIRE OR SMOKE. MAINTENANCE INSPECTED THE AREA, FOUND NO EVIDENCE OF HEAT, FIRE OR SMOKE. FOUND TO BE AN INDICATION PROBLEM. REMOVED AND REPLACED DETECTOR, SMOKE DETECTOR AMPLIFIER. OPS CHECK NORMAL PER MM 26-16-11. AIRCRAFT RETURNED TO SERVICE. REFERENCE TWRA96178.