E/P Positioner

There is one problem with positioner, after giving air supply same pressure showing at positioner output, so i think positioner is not working. So can I replace the flapper nozzle & diaphragm part from other positioner as we don't have same type of positioner, is it possible to replace that parts?

Why do you think that supply pressure at the positioner output is a problem?

The output pressure is determined by the internal positioner controller according to its setpoint (process control signal to the
positioner) and its process variable (the present position of the valve stem).

If the position is reported at one extreme and the setpoint at the other extreme, then that is a maximum error to the positioner controller and the output response is to provide as much output pressure as possible to reduce the error.

If you had an E/P transducer, one would not expect supply pressure at the outlet unless the supply pressure was too low; less than the presumed modulated output pressure. But you used the word 'E/P positioner', not E/P transducer.