What was found
OBERSERVOR O2 MASK HAS LEAK. STARTED IN CRUISE COULDN€™T STOP LEAK. (FLIGHT 6064 - FILED CLOSED)REMOVED AND REPLACED CREW OBSERVER OXYGEN MASK ASSY IN REFERENCE TO AMM 35-11-12. REMOVED AND REPLACED CREW OBSERVER OXYGEN MASK STOWAGE BOX ASSY IN REFERENCE TO AMM 35-11-15. PERFORMED LEAK CHECKS OF CREW OBSERVER OXYGEN MASK STOWAGE BOX AND MASK ASSY AS REQUIRED. LEAK CHECK GOOD AT THIS TIME. PERFORMED OPERATIONAL CHECK OF CREW OXYGEN SYSTEM IN REFERENCE TO AMM 35-10-00. OPS CHECK GOOD AT THIS TIME. AIRCRAFT OK FOR SERVICE. REF EAML 1866326 FOR CREW O2 BOTTLE REMOVAL AND REPLACEMENT.