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Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
Pneumatics Control Module 270
Replacement procedures
2. Remove the detector cover, the pneumatics cover, the inlet fan cover, the
inlet cover (or tray mounting bracket), and the left side cover.
3. Starting at the PCM, trace each line of the gang weldment from the
pneumatics block to the end connector. Disconnect each line.
4. Remove the screw in the plumbing block and remove the gang weldment
from the PCM.
5. Replace the gang weldment and O-rings. Reassemble in reverse order.
6. Check for leaks.
Calibrating the PCM interface
The interface's flow module contains a pressure sensor that must be zeroed
after it is installed on the GC. Calibration ensures an accurate interface
pressure display.
Do not connect the carrier gas to the flow module until you have zeroed the
interface's pressure sensor.
1. If the gas supply is connected to the GC, turn off the supply at the source,
then disconnect the supply line from the PCM inlet fitting.
2. Turn on the GC and wait 15 minutes to allow it to reach thermal
equilibrium.
3. When the GC has reached thermal equilibrium, press [Options], scroll
to Calibration and press [Enter].
4. Scroll to Front inlet or Back inlet and press [Enter].
5. Scroll to Pressure Zero.
6. Press [On] to zero the pressure sensor.
7. Turn off the GC.
8. Plumb the carrier gas to the flow module.
9. Turn on the GC.
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