What was found
DURING CRUISE, EN ROUTE FROM PHL TO ORD, CREW REPORTED THE AUTO PRESSURE CONTROL FAILED AT FL340. CABIN ALTITUDE CLIMBED TO 10,000 FEET AND THE WARNING HORN SOUNDED. CREW ACCOMPLISHED AN EMERGENCY DESCENT TO FL240 AND SELECTED STANDBY MODE WITH BOTH PACKS IN HI-FLOW MODE. UPON REACHING FL240, PRESSURE CONTROL REMAINED SATISFACTORY. FLIGHT CONTINUED AND LANDED WITHOUT FURTHER INCIDENT AT ORD. MAINTENANCE REMOVED AND REPLACED THE AT CARGO DOOR SEAL. ALSO, REMOVED AND REPLACED THE OVERHEAD PRESSURIZATION PANEL, PRESSURE CONTROLLER, AFT OUTFLOW VALVE AND EQUIPMENT COOLING PRESSURE REGULATOR VALVE. ALL OPERATIONAL CHECKS AND LEAK CHECKS GOOD.