What was found
RT AIR MIX VALVE STUCK FULL COLD. FOLLOWED BY LOSS OF CABIN PRESSURIZATION. RAN PACKS INDIVIUALY AND TOGETHER. PERFORMED LEAK CK OF DUCTS, PACKS, MIX VLVS. NO DEFECTS NOTED. PERFORMED BITE TEST OF 35 DEG VALVE AND WATCHED VALVES OPERATE. PULLED C/B ON PACK FANS AND CHECKED FOR INTERNAL LEAKS OF THE HEAT EXCHANGERS. ALL CHECKS GOOD. PERFORMED PRESSURAZATION CHECK USING APU THEN NR 1 & 3 ENGINES. COULD NOT DUPLICATE, REF JRH CHAPTER NR 8, AS A PRECAUTION R & R LT & RT COALESCER BAGS REF MM 21-55-051-4, LEAKED CHECKS GOOD. NO HISTORY, OK FOR SERVICE. R & R RT MIX VALVE REF MM 21-61-011-4, PERFORMED OPS CHECK OF RT MIX VALVE IAW MM21-61-011-4, OPS CHECKS GOOD AT THIS TIME.