HP 5890 Series II Plus Reference Manual page 179

Preventive Maintenance
Nitrogen-phosphorus detector (NPD)
Turn off the detector and its heated zone; also turn off gases to the
detector (particularly H ! ). Allow time for the detector zone to cool. Open
the top cover at its front edge to access the detector.
1. Using a Pozidriv•typescrewdriver, remove three screws around the
detector cover and carefully remove the cover (see Caution below).
Caution Note that the transformer supplying power to the active element is
secured to the inside of the cover. It may be left in place, but be
careful not to stress its leads, either those to the collector, or those to
the detector signal board.
Figure 8-15
NPD Collector Assembly
Active Element
Active Element Transformer
NPD Collector and Active Element Power Supply Transformer
Wear proper eye protection when using compressed gas for cleaning
WARNING
purposes.
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