Replacing The Photomultiplier Tube - Agilent Technologies 6890 Series Service Manual

350 Flame Photometric Detector (FPD)
Replacement procedures
12. Carefully replace the fused silica liner, ferrule and tube onto the detector
base. The fused silica liner should be positioned so that it protrudes
3 to 6 mm (1/4-inch) above the top of the transfer tube weldment. With
a wrench, firmly tighten the transfer tube 1/2-turn past finger-tight.
13. Reinstall the heated block, the heater/sensor cable assembly, the nut, and
the ferrule. The notch in the bottom of the block fits over the tubing
coming from the detector fitting.
14. Tighten the U-clamp screws, then tighten the nut on the transfer tube.
15. Place the detector on top of the instrument, orient it properly, and install
the four screws to hold it. Install the top cover and the exhaust tubing.
16. Connect the ignitor cable to the printed circuit board.
17. Install the PMT assembly (or assemblies).
18. Restore normal operating conditions.

Replacing the photomultiplier tube

If the PMT is defective (high voltage on and the flame lit: low or no signal
and/or high noise not attributed to any other source such as bad cables, light
leaks, high temperature, defective signal board, etc.), it must be replaced.
1. Turn off power to the gas chromatograph and disconnect the main power
cord.
Caution Turn the electrometer or main power off before opening the PMT housing to
avoid destroying the tube.
2. Free the cables to the PMT from the clip on the support. Pull a few inches
of the cables through the cable tie toward the end cap. Unscrew the end
cap from the PMT assembly. Slide the cap away from the assembly.
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Detectors
Agilent 6890 Gas Chromatograph Service Manual
Jun 2001