What was found
*S/D* PDX - AIR TURNBACK - AUTO PRESSURIZATION PREVIOUSLY PLACED ON MEL 21-14 (12/28/2000); AFTER TAKEOFF FROM PDX, STANDBY PRESSURIZATION FAILED AND CREW WAS UNABLE TO CONTROL CABIN PRESSURE IN NORMAL MODE; THE AIRCRAFT RETURNED TO PDX. IN PDX PRESSURIZATION INTEGRITY CHECK WAS PERFORMED PER AWA TASK CARD F1B21006 AND NO FAULTS NOTED; THE CABIN PRESSURE CONTROLLER WAS REPLACED AND FUNCTIONAL CHECKS WERE GOOD; MEL 21-14 WAS CLEARED AND THE AIRCRAFT WAS RETURNED TO SERVICE, NO FURTHER FAULTS HAVE BEEN REPORTED AS OF 1/12/01.