Detector Overview; About The Detector Signal Boards - Agilent Technologies 7820A Service Manual

Detector overview

About the detector signal boards

40
Agilent 7820 GC Service
A detector monitors the gas stream exiting from the analyzing
column. Its electrical output changes when the composition of
the gas does. This section deals with the most widely used
detectors.
The GC can control up to 2 detector signal boards and
simultaneously process their digital signals. All detector boards
are mounted in the electronics carrier on the right-hand side of
the GC.
Sometimes other problems seem like a signal board failure.
Replace a signal board only after ruling out other possible
causes as follows:
1 Verify the signal board is receiving 24 VDC power, the green
LED is ON, and the board appears configured in the GC
display.
Check diagnostics for faults caused by components connected to
the signal board, such as, ignitors, electrometers, filaments, and
PMTs.
Replace the signal board only after eliminating the possible
causes listed in steps 1 and 2.
Repairs should be verified by the following:

Typical detector signal baseline output and noise.
The types of detector signal boards, along with part numbers and
possible locations, are listed in the table below.
Table Detector signal boards
Descriptio Part number
n
uECD G3433-60020
FID G3431-60020
NPD G3434-60021
TCD G3432-60015
Slot
F-DET or B-DET
F-DET or B-DET
F-DET or B-DET
F-DET or B-DET