Preventive Maintenance

Nitrogen-phosphorus detector (NPD)

Caution Do not overtighten the jet! Overtightening may permanently deform and damage the jet, the detector base, or both.

8.Replace the NPD collector, and transformer and cover assembly. Be certain the spring contact to the signal board is in good contact with the groove on the collector (see Figure 8•13).During reassembly do not touch the lower portion of the collector assembly because fingerprints and/or other contamination may (will) cause baseline drift and/or noise.

Removing/replacing the NPD collector

Figure 8-16

Collector Body

NPD Collar

NPD Active Element

Note Position of Collector

Cross-Section, Assembled Type A NPD Collector

181