What was found
SHORTLY AFTER REACHING CRUISE ALTITUDE OF FL410, AN AUDIBLE POP WITH ASSOCIATED RISE IN CABIN PRESSURE OCCURED. WE STARTED DESCENDING AND CABIN ALTITUDE AMBER CAS DISPLAYED AND QRH WAS ACCOMPLISHED. ACM O'HEAT AND HEAT EXCHG ONLY DISPLAYED UNTIL QRH PROCEDURE CLEARED MESSAGE. LANDED WITHOUT FURTHER ISSUE. PRESSURIZATION SYSTEM IS CONSIDERED INOP. INSPECTED TAIL COMPARTMENT FROM FS 526.2 TO FS 691.8 AND FOUND MIXING ASSEMBLY TO BE SEPARATED AT ITS AFT WELD. REMOVED MIXER ASSEMBLY AND REPLACED WITH NEW, P/N: 7415724-50, IN ACCORDANCE WITH CESSNA 700 MM 21-50-05. VERIFIED TT133 DUCT SENSOR IS CLEAN. COMPLIED WITH TAIL CONE CONDITIONED AIR MUFFLER ASSEMBLY ADJUSTMENT/TEST. LEAK AND OPERATIONAL CHECK S GOOD.