PTV on 7890 GC-ECD giving low response and not maintaining pressure ramp with set point

The PTV on my 7890 GC-ECD is giving me low response and will not maintain pressure ramp with the setpoint when I do a run. I have tired changing the syringe liner, ferrule, and glass wool. I also clipped the column at the inlet and the detector. Can someone please help?

  • Good morning CM,
    In answer to your questions, the supply pressure for the carrier gas(helium) coming in is ~55-60 psi.
    The PTV inlet pressure holds at 6 psi prior to the start of a run, but as soon as the temperature starts ramping, the pressure drops to about 5.1 psi and at that point will no longer maintain the pressure with the ramp. Is it possible that there could be a leak in the inlet?(I will check for a leak this morning and let you know.
    As for the low response from the ECD, I made the following changes, however none of these changes seemed to resolve the issue:

    <![if !supportLists]>-          <![endif]>Changed inlet liner and glass wool

    <![if !supportLists]>-          <![endif]>Changed inlet ferrule

    <![if !supportLists]>-          <![endif]>Clipped column at inlet and detector

    The idle output signal from the ECD is ~100, indicating that the ECD is “healthy”.
    I have not tried baking out the ECD and I am planning on trying that today.
    I will let you know how everything goes.
    Brian B. Barnes, Ph.D.
  • Good morning  

    Thank you for the details.

    You can definitely do a leak check, I will leave below a link that describes the procedure. Is your method split or splitless?

    Using the 7890 Service Mode Leak Check (

    Let me know what your findings are.

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