What was found
DURING TAKEOFF CREW REPORTED RT ENGINE N3 INDICATION WAS ERRATIC. DURING CLIMB RT ENG BLEED VALVE WAS CYCLING OFF & ON, ACFT DID NOT PRESSURIZE. CREW TURNED OFF RT ENG BLEED & ACFT BEGAN TO PRESSURIZE. RETURNED TO DEPARTURE & EMERGENCY DECLARED. LANDING UNEVENTFUL. REMOVED AND REPLACED RIGHT ENGINE N3 TACH TRANSMITTER IAW AMM 77-12-02 AND CONNECTOR BACKSHELL IAW WDM 71-51-22. ACCOMPLISHED RIGHT ENGINE RUN. SYSTEM CHECKED NORMAL IAW AMM 71-00-00.