What was found
DFW - FLT 499 - DURING DESCENT AT FL330, CABIN ALTITUDE LIGHT ILLUMINATED. CREW EXPEDITED DESCENT AND AT FL12 ALL OXYGEN MASKS DEPLOYED. AIRCRAFT LANDED DFW WITHOUT FURTHER INCIDENT. MAINTENANCE ACCOMPLISHED RATE CHECK AND GROUND PRESSURIZED AIRCRAFT IN AUTOMATIC/MANUAL MODE WITH NO ABNORMAL CONDITIONS NOTED. ALL REQUIRED CHECKS WERE PERFORMED WITH NORMAL OPERATION. UNABLE TO DUPLICATE FAULT. REPLACED OXYGEN GENERATORS AND REPACKED MASKS. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)