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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.
Released: April 2004
Figure 1-24. FPD Photomultiplier Tube
3. Slide the resistor network cable assembly
6850 Series Gas Chromatograph Service Procedures
Unscrew the end cap from the PMT assem-
bly. Slide the cap away from the assembly.
Resistor network cable assembly
Tube socket
Photomultiplier tube
(PMT) Replacement
and the photomultiplier tube and socket out
of the housing until about 1 inch of the tube
is exposed.
End cap
PMT tube housing
189
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