What was found
COULD NOT MAINTAIN PRESSURIZATION ON NR 1 PACK AT 25K, DIFFERENTIAL UP TO 7PSI ON CLIMB BUT SLOWLY LOST PRESSURIZATION TO 3 PSI; COULD ONLY MAINTAIN 7K AT 15K ALTITUDE. LOST COMPLETE PRESSURIZATION AT 4K ALTITUDE, AUTOFAIL & STANDBY LIGHTS, TRIED TO MANUAL VALVE CLOSE, WOULD NOT WORK. WORKED ON DECK AFTER LANDING. PERFORMED PRESSURIZATION CONTROLLER SYS ADJUSTMENT AND TEST IAW AMM 21-31-000-5 PAR B, C, D. CONTROLLER FAILED TESTS B2C1 AND 2-DC, MANUAL MODE FLT OPS. ALSO FAILED C2C1 AND 2-AC MANUAL MODE FLT OP TEST. PERFORMED STBY MODE TEST AND FAILED STEP G -AIRPLANE BAROMETRIC CORRECTION TEST D2G2. OUTFLOW VALVE FAILED TO OPEN OR CLOSE. PERFORMED PRESS SYS TEST IAW AMM 21-31-000-2-0 AND TESTS PASSED. REMOVED AND REPLACED CABIN PRESSURIZATION CONTROLER AND OPS CHECKED GOOD IAW 727AMM 21-31-000-2 AND 21-31-0005.