What was found
AIR ENGINE NR 1 AND NR 2 BLEEDS FAULTED AT FLIGHT LEVEL 390. STARTED LOSING CABIN PRESSURIZATION, ATC CLEARED AND EXECUTED RAPID DESCENT, DURING WHICH CABIN ALTITUDE WENT TO 12500 FEET. BLEEDS RECOVERED AT 10,000 FEET. MASKS WERE NOT DROPPED, AND AIRCRAFT LANDED UNEVENTFULLY AT DESTINATION. NR 2 BLEED, FAN AIR VALVE AND PNEUMATIC TEMP CONTROL THERMOSTAT (TCT) REPLACED. NR 1 BLEED, BLEED MONITOR COMPUTER (BMC) REPLACED. CHECKS NORMAL.