What was found
CREW REPORTED LOSS OF CABIN PRESSURIZATION AT FL330. CREW MANUALLY DEPLOYED PAX O2 MASK AT 12,100 FT WITH CABIN ALT SHOWING 20,000 FT IAW ENGINEERING INSTRUCTIONS AND ASSISTANCE MX R & R THE DIGITAL PRESSURIZATION CONTROLLER, CABIN PRESS. AQUISITION MODULE (CPAM), ELECTROPNEUMATIC AND PNEUMATIC OUTFLOW VALVES ALONG WITH AFFECTED O2 MASKS AND GENERATORS. OPS CHECKS WERE SUCCESSFUL AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE.