What was found
FLT 2015 - BIL-DEN - DURING CLIMB, SMOKE FROM THE FIRST OBSERVERS OXYGEN REGULATOR WAS NOTED. CREW RETURNED TO BIL AND MADE A SAFE LANDING WITHOUT ANY FURTHER INCIDENTS. MAINTENANCE INSPECTED AND FOUND BURNED SPOT ON OXYGEN REGULATOR LIGHT PANEL. PROBABLE SHOR IN OXYGEN PANEL. REMOVED AND REPLACED OXYGEN REGULATOR PER B727-287 AMM 35-11. OPERATIONAL CHEC OK. AIRCRAFT WAS RETURNED BACK TO SERVICE. (M)