What was found
AT 35,000 CABIN ALT WARNING HORN SOUNDED. CABIN ALTITUDE WAS APPROX 10,500 & CLIMBING AT 500 FPM SLOW DEPRESSURIZATION. INITIATED DESCENT, SELECTED LOWER ALT. CABIN GOT UNDER CONTROL & STARTED DESCENDING. FOUND 2 INCH PIECE OF OUTFLOW VLV SEAL MISSING. R & R OUTFLOW VLV IAW MM 21-31-03-402-010 & ALSO FOUND LT PACK CONTROLLER FAILED. REPLACED LT PACK CONTROLLER IAW 21-51-14. PERFORMED EXCESSIVE CABIN LEAKAGE TEST IAW 05-51 -24-702-001 & FOUND NO FAULTS. ACFT OK FOR SERVICE. ROTABLE PARTS CHANGE WAS INDICATED, TT 1664320 SN OFF 02132, TT 1672438 SN OFF 02350 VLV, AIR, CAB OFF 99-2131-9-0004 2132 ON 99-2131-9-0004 2670 CONTROLLER, PAC OFF 53-2151-9-0001 2350, ON 99-2151-9-0005 4853.