FID fault

Hi all,

The 7890B GC shows Back detector fault. The FID is reading 5.6 E06 pA.

The GC is installed within a glove box and access is limited and maintenance cannot be performed.

Any ideas? I had recently also a failure on a trace heating controller (trace heating installed on a custom made FID chimney) and i think it might be electrical issue.

Thank you,


Parents Reply
  • One common cause of this is the electrometer is grounding somewhere.  Often it is due to the spring at the end of the interconnect assembly is not resting correctly inside the groove on the collector itself.  If you can remove the entire collector assembly and the signal drops to zero, there is a problem with the collector assembly.  Either dirty/contaminated as ISH suggests or not assembled correctly.  If the signal stays high, that points to an electronics problem, either interconnect, electrometer, or signal board.  I know you said access to the GC is limited but I think this is the easiest way to diagnose the problem.

    More details on FID maintenance, see the 7890 Maintenance manual starting on page 195:

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