What was found
ON INITIAL TAKEOFF ROLL EN ROUTE, THE CABIN CLIMB INDICATOR NEEDLE WENT TO RAPID RATE OF DESCENT OF ABOUT 4000 FPM, REJECTED TAKEOFF AND RETURNED TO GATE. MAINTENANCE REMOVED AND REPLACED THE CABIN PRESSURE CONTROLLER IAW BMM 21-31-21, PERFORMED OPERATIONAL CHECK IAW T/C F1B21001. RAN ENGINE AT TAKEOFF POWER, AIRCRAFT PRESSURIZATION WAS NORMAL. VENDOR FUNCTIONAL TEST OF CABIN PRESSURE CONTROLLER, CONFIRMED FAILURE OF UNIT. R & R 2 CAPACITORS. UNIT WAS TEST AND RETURNED TO SERVICE IAW CMM 21-31-11, REV. 13.