What was found
CLT - FLT 12 - EN ROUTE FROM MCO TO PHL, AT APPROXIMATELY FL190, THE CREW HAD DIFFICULTY MAINTAINING CABIN PRESSURIZATION. MAINTENANCE CONTROL WAS CONTACTED FOR TROUBLESHOOTING BUT THE PROBLEM CONTINUED. FLIGHT DIVERTED TO CLT AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE FOUND THE SWING CHECK VALVE, FOR THE EXTERNAL GROUND CONDITIONED AIR, BROKEN AND DISPLACED. REMOVED AND REPLACED CHECK VALVE ASSEMBLY. PRESSURIZATION CHECK GOOD. (M)