What was found
DURING FLIGHT, AIRCREW NOTICED THE NR1 FMS SMOKING AND THEN FAILED. GROUND MX CREW REMOVED THE NR1 FMS, INSPECTED THE WIRING AND SURROUNDING COMPARTMENT, RE-INSTALLED THE FMS. DISCREPENCY WAS MEL'D, THE IRU-1 C/B WAS PULLED AND COLLARED. GROUND MX CREW R & R THE NR1 FMS, REMOVED C/B COLLAR AND CLOSED C/B. OPS CHECK WAS PERFORMED SATISFACTORY, ACFT WAS THEN RETURNED TO FLIGHT STATUS.