Thermal Conductivity Detector (Tcd); Replacing The Tcd Detector Cell - Agilent Technologies 7820A Service Manual

Thermal Conductivity Detector (TCD)

Agilent 7820 GC Service
81
The TCD is sometimes called the "universal" detector because it
responds to anything that is not the carrier gas.

Replacing the TCD detector cell

1 Cool down the oven.
Turn off the GC main power switch and disconnect its power
cord.
Hazardous voltages are present in the
mainframe when the GC power cord is connected.
Avoid a potentially dangerous shock hazard by
disconnecting the power cord before removing
any GC panels.
Components can be damaged by static electricity:
be sure to wear an ESD strap grounded to the GC
chassis while performing this procedure.
Turn off any detector gases at their supply.
Shut off the detector and the detector gases and let the detector
cool.
Remove the detector cover, the electronics top cover, and the
pneumatics cover.
Disconnect the TCD filament leads which run from the detector
to the detector interface card. Disconnect the wires from the
detector interface card using a small flat blade screwdriver to
push down on the connector tabs while you pull out the wires.
Remove the cover and the insulation.
Use a T-20 Torx screwdriver to remove the two screws securing
the detector cell to the aluminum detector carrier bracket and lift