HP 5890 Series II Plus Reference Manual page 182

Preventive Maintenance
Nitrogen-phosphorus detector (NPD)
Figure 8-17
Type A
NPD Collector and Collector Assembly
Whenever the collector must be removed from the detector cover of a Type
A NPD, the following procedure should be used:
Note: During disassembly do not touch the lower portion of the collector
assembly. Use clean, lint•freegloves to prevent contamination of the
assembly. Suitable gloves (HP Part No. 8650•0030)are available.
1. Following the procedure under Cleaning, remove the collector
assembly from the detector base. A 1.5•mmhex wrench is required for
disassembly.
2. Loosen the setscrew in the brass collar at the top of the collector
assembly. Remove the transformer lead from the collar; then remove
the collar itself.
The remaining transformer lead does not need to be disconnected to
remove the collector. However, if desired, it is easily removed by
loosening the setscrew in the stainless steel portion of the collector
body.
182
Type B
Detector
Cover
Trans-
former
Brass Collar
Teflon Spacer
Transformer Strap
Steel Spring
Spacer
Collector
O-ring
Collector Body