What was found
AFTER LEVEL OFF AT FL 240 WITH SINGLE PACK OPERATION, LEFT CABIN ALTITUDE CONTINUED A 200 FPM CLIMB. UNABLE TO CONTROL BY ALTERNATE MEANS. FLIGHT JETTISONED 10,000 LBS OF FUEL, DIVERTED TO MSP AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED AUTO PRESSURE CABIN CONTROLLER. OPERATIONAL CHECK NORMAL.