What was found
CLIMBING THROUGH APPROX FLIGHT LEVEL 340 SIGNIFICANT PRESSURE CHANGE, EARS POPPED, NO CAUTIOIN LIGHT, STOPPED CLIMB, STARTED DECENT, RAN UNCONTROLLED PRESSURE CHECLIST. REGAINED CONTROL WITH SELECTOR TO ALTN DIFF PRESSURE PEAKED AT 8.8. CONTINUED WITH NORMAL OPERATION. GROUNDED - YES. (RESOLVED ON W/O: 1972399 TASKCARD: N/R-00001 ) REMOVED & REPLACED #1 CABIN PRESSURE CONTROLLER REF AMM 21-31-01. PERFORMED PRESSURIZATION GROUND TEST REF AMM 21-31-00. NO DEFECTS NOTED. THIS CLEARS MEL 21-14C. C/N 09006512 REMOVED. SEAMC SCOTT NOTIFIED.