As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(ATB TO ANC) LEFT AC PACK TRIP ANNUNCIATION OCCURRED FOLLOWING TAKEOFF AND COULD NOT BE RESET. AIRCRAFT CABIN PRESSURIZATION DROPPED TO 12K FEET ONE HALF HOUR INTO FLIGHT AT FL350 AND ALTITUDE WARNING HORN SOUNDED. PAX OXYGEN MASK DID NOT AUTO DEPLOY BUT FLIGHT CREW DONNED OXYGEN MASKS. DESCENDED AND RETURNED TO ANC. REPLACED DEFECTIVE TEMPERATURE CONTROL VALVE AND A RUPTURED FLEXIBLE DUCT BETWEEN THE CONDENSER AND THE HPWS MIX MUFF IN RT AIRCON BAY.