What was found
ACFT WAS BEING VECTORED WHEN THE PRESSURIZATION BECAME ERRATIC, COULDN'T GET IT UNDER CONTROL MANUALLY AND FINALLY PRESSURIZATION DEPRESSURIZED AT 5000 FEET. ACFT LANDED AND MAINTENANCE, R THE ELECTROMAGNETIC OUTFLOW VALVE IAW AMM 21-31-03; IPC 21-30-00, FIGURE 30, ITEM 160. R & R THE PNEUMATIC OUTFLOW VALVE IAW AMM 21-31-04;IPC 21-31-00, FIG 30 ITEM 1. ALSO. REPLACED THE DIGITAL CONTROLLER IAW AMM 21-31-01, FIG 04 ITEM 10.OPS CHECK GOOD AND WAS RELEASED. PN OF DIGITAL CONTROLLER 2099L02110, SN 01668. PNEUMMATIC OUTFLOW VALVE, PN 2097K011100 AND SN 01522.