Thermal Conductivity Detector (Tcd); Remove/Replace Tcd Detector Weldment - HP 5890 SERIES II Service Manual

THERMAL CONDUCTIVITY DETECTOR (TCD)

The main portion of the TCD detector is a heated block into which a heater cartridge and two sensor
cartridges are installed. In addition to the standard heater and sensor cartridges, a second sensor car-
tridge (referred to as the delta- t cartridge) is employed which is connected to the TCD detector PCB. If
the detector requires replacement, the entire assembly is replaced as a unit.

Remove/Replace TCD Detector Weldment

HAZARDOUS VOLTAGES ARE PRESENT IN THE INSTRUMENT WHEN THE POWER
CORD IS CONNECTED. AVOID A POTENTIALLY DANGEROUS SHOCK HAZARD BY
DISCONNECTING THE POWER CORD BEFORE WORKING ON THE INSTRUMENT.
1. Set the main power line switch to the off position.
2. Disconnect the power cable from its receptacle.
3. Allow time for the oven and heated zones to cool.
4. When the heated zones are cool, turn off all gas
supplies.
5. At the bottom of the detector(s) to be removed,
inside the column oven, remove the column
and hardware associated with the detector(s)
(liner, column/liner nuts, ferrules, makeup gas
adapter,etc.).
6. If the detector is not going to be replaced with a
new detector, cap the detector base.
7. Lift the hinged top cover at its front edge,
exposing the detector area.
8. Remove the TCD detector cover by removing
two screws: one from each side of the detector
cover.
9. If the detector is not going to be replaced with a
new detector, cap the TCD vent port on the top
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SCREW
SVC 4- 4
RED O VISIBLE
OFF ON
TOP COVER
SOLENOID
VALVE
DETECTOR
COVER