Replacing The Npd Electrometer - Agilent Technologies 7820A Service Manual

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Agilent 7820 GC Service
Remove the four T-20 screws retaining the NPD assembly to the
GC.
Remove the NPD detector assembly from the GC.
Examine the underside of the detector assembly.
Cover or plug the sample inlet tube while servicing this unit to
limit contamination.
Remove the insulated cover over the heater/detector block.
Loosen the heater cable sufficiently to allow for the lifting off and
removal of the heater from the detector block.
Remove and replace the entire heater/cable assembly.
Reassembly is the reverse of these steps.

Replacing the NPD electrometer

1 Cool down the oven.
Turn off the GC main power switch and disconnect its power
cord.