Troubleshooting
6850
6850
Released: April 2004 6850 Series Gas Chromatograph Service Procedures 301
• Clean or replace the FID jet (better to
replace)
• Clean or replace the FID collector and Teflon
insulators (better to replace)
• Inspect the underside of the brass castle
assembly for rust or corrosion and replace if
dirty
• When reassembling the FID make sure that
all mechanical assemblies are tight and that
the interconnect spring does not get
deformed. It should be oriented into the
channel on the outer perimeter of the FID
collector.
• Plug the FID column fitting to continue with
the troubleshooting procedure.
7. Relight the flame and bakeout the detector
at 350°C for an hour.
8. Re-evaluate the FID noise and background at
normal FID and GC oven operating tempera-
ture.
If the noise or background is still too high, the
Air, H
2
and Makeup gas purity is suspect. The
FID can be operated with just Air and H
2
. Turn
off the makeup gas and reevaluate the FID noise.
If there is a significant drop in noise or back-
ground (>5 pA drop in background) then the
makeup gas purity is suspect. Try replacing or
installing traps in the makeup gas supply as
outlined in the overview. If the problem persists
then try installing/replacing moisture traps in the
H
2
and Air supplies or try alternate sources for
H
2
and Air.
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