HP 5890 Series II Plus Reference Manual page 185

Preventive Maintenance
Nitrogen-phosphorus detector (NPD)
4. Remove the collector from the collector assembly as follows:
5. The jet can be removed for cleaning or replacement (if the jet is very
dirty it should be replaced) with the 1/4•in.nutdriver supplied with
the instrument. Using the nutdriver, unscrew (turn jet
counterclockwise) and remove the jet from the detector base.
The detector should be cold and the instrument unplugged to avoid the
Caution
danger of the flammable solvents flashing and possibly igniting the
fumes.
Loosen the 1.5•mmscrew holding the transformer secondary wire to the
top of the collector and disconnect the wire. The hex key wrench required
is a 1.5•mmsize and was provided with the instrument.
Loosen the 1.5 hex key screw holding the brass connector to the collector
top and remove the brass connector.
Remove the Teflon spacer and the stainless steel spacer/spring from the
top of the collector body.
Loosen the 1.5•mmhex key screw holding the collector into the collector
body and pull the collector out the top of the collector body. Grasp only
the top portion of the collector to avoid contamination. If you plan to
reinstall the collector, lay it aside on a clean surface until ready for
reassembly. See below for cleaning instructions.
The jet exists in two sizes: 0.018•in.and 0.011•in.id. A cleaning wire
may be used to help remove deposits from the bore of the jet (jet cleaning
wire, Part No. 18765•20070is 12 inches of 0.016 od wire that can be used
for this purpose).
Wash both the bore and the exterior of the jet with a 1:1 (V/V) solution of
methanol and acetone. The jet may also be cleaned in an ultrasonic bath
in the same solution. It is best to dry the jet and bake it out in an oven
(70 to 150 C) before replacing it in the detector. After cleaning, apply a
small amount of lubricant to the threads of the jet. The lubricant is
necessary to prevent galling of the threads in the detector base.
The detector base may be cleaned using solvents (such as used for the
jet), a cleaning swab, or wire brush, and dried with low•pressure
compressed air.
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