As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) OVERHAULED SECONDARY OUTFLOW VALVE FOR PRESSURIZATION SYSTEM WAS INSTALLED TO RECTIFY A POPPED CIRCUIT BREAKER. SYSTEM GROUND RUN CARRIED OUT AND AIRCRAFT DEPARTED A FEW DAYS LATER. UPON REACHING FL 230 FT PNF NOTICED CABIN PRESSURIZATION WAS AT MAX CABIN DIFFERENTIAL 8.8 POUNDS. THE CABIN ALTITUDE INDICATED SEA LEVEL "O". AIRCRAFT RETURNED TO POINT OF DEPARTURE. ANOTHER SECONDARY OUTFLOW VALVE INSTALLED AND GROUND CHECKED SERVICEABLE.