What was found
INFLIGHT, RT PACK TRIPPED OFF, ATTEMPTED TO RESET, NO HELP. TRIPPED AGAIN AND NOTED LIGHT SMOKE. AIRCRAFT RETURNED TO LAS AND MADE AN UNEVENTFUL LANDING. CHECKED SYSTEM FOR LEAKS, RT AIR CYCLE MACHINE, TURBO FAN AND ALL RELATED PACK COMPONENTS AND OPERATED PACK NORMALLY PER BOEING M/M.