What was found
AIRCRAFT PERFORMED AN UNSCHEDULED LANDING AS A CONSEQUENCE OF BOTH CABIN PRESSURE CONTROL VALVES WERE OUT SERVICE AND CABIN ALTITUDE ROSE TO 9500. IT WAS NECESSARY TO CONTROL PRESSURE IN MANUAL DUE TO AN OBSTRUCTION OF WHEEL CONTROL. IN GROUND, BOTH SYSTEM WERE CHECKED AND WORKED NORMAL IAW MM 21-32-03. DURING OVERNIGHT SERVICE, THE OUTFLOW VALVES BODY WAS REPLACED, ADJUSTED AND TESTED. RIGGING WAS PERFORMED TO CABLES 119-B AND 120-B IAW MM 21-32-05, TESTED CORRECT. A PRESSURIZATION TEST WAS PERFORMED 3 TIMES IN MANUAL AND AUTOMATIC, ALL CORRECT.