As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, CABIN PRESSURE DIFFERENTIAL INCREASED TO 5 PSI AND CABIN ALTITUDE DROPPED TO 0 MSL. COULD NOT CONTROL WITH MANUAL CONTROLLER. RETURNED TO SLC. PERFORMED OPERATIONAL CHECK OF MANUALLY CONTROLLED OUTFLOW VALVE IAW MM 21-30-00. OPS CHECK GOOD.