there is no emission current


i am using a gc/ms 5975C inert xl ei/ci msd. all the filament i m using is giving me these information 'there is no emission current' just after 2 hours of using a new filament. please can any body help me to check what is going wrong to damage my filamant all the time?

  • Hello , the first thing I would do is try the other filament if this is on an EI source; this should help confirm that the problem is actually with this particular filament or its wiring and not a broader electronic or other problem. If it's a CI source, it only has one filament of a different design from the EI filaments and there's a “dummy” filament that provides connections for the filament 2 wires.


    The reasons for failure could be many, but among them are:

    • The connection of the filament was loose when installed or grounded to the source body. Ensure that it's connected properly. Below is a wiring diagram for the feedthrough board:

    • The filament was bad and indeed it failed after 2 hours; was it bought from Agilent directly?
    • There's a vacuum leak in the analyzer; if you have an ion gauge, what is your vacuum level (i.e., ion gauge pressure)?
    • The source might need to be cleaned.
  • I have same problem.

    I cheked both of filament are ok.

    Filament 1 turn on for 3 second and then turn off.

    Second filament don't have same problem.

    It is ok.

    What is the reason?

  • We changed the filament with each other.

    And problem is still exist. It shows that the problem is not from internal.

  • "No Emission Current"    -- This message just says that the filament is not working. 

    Wait long enough after pumping down. Don’t turn on the MS to just ‘take a look’ to see how the pump down is going.  The residual oxygen damages the filament immediately….a tiny, unrecoverable, bit.  Wait long enough, like a full hour before even thinking about turning on the filament. Use the ion gauge reading, remembering that as the ion gauge filament ages its measurements aren’t as good, either.  The ion gauge is also calibrated for nitrogen, not helium or hydrogen, both of which are much harder to pump away.  

    ( Helium- take the gauge reading and divide it by 0.18.  Hydrogen – take the gauge reading and divide it by 0.46 ) 

    Wait long enough  --=-- your patience will be rewarded with longer filament life.

    Make sure and use long enough solvent delay.  If the filament is on when the solvent peak comes through, the increased ion source pressure from all of those solvent molecules can damage the filament. 

    Sometimes you have to replace both filaments – even if one was rarely used.  The filaments sit immediately next to two of the holes where sample molecules exit the ion source chamber.  It’s good practice to run the unused filament sometimes. Create a Atune_F2.U tune file and tune on F2.  

    When you are cleaning the ion source and have it apart, use a solvent dipped swab to wipe the filament insulators as residue can stick there.  The filament will not work properly if the filament insulator is contaminated and not insulating.

    Depending on where one filament fails, you may or may not be able to use the spare filament.  If the filament breaks and touches the reflector, the circuitry will not be able to compensate, and you’ll have to vent and replace at least the broken one.

    Make sure that the entire ion source is clean – every surface, edge, hole, window, nook, cranny, face, etc…inside and out.  Make sure that the area near the filaments and the electron beam holes are cleaned every time, too. That area is important to the filament drive.

    If the instrument has been well utilized and has had the source cleaned many, many times, the ceramic source connector board wire connectors may be loose. When you press the connectors onto the filament posts, do they feel like they are making good contact or do they sort of slide on and then slip around?

    Go into Manual Tune, set the emission current to about ½ of the typical autotune setting – around 17. Then do repeat profile or scan. Does it turn on then?  It could be that a system can’t drive to 34.6, for example, but can drive ½ way to 17.  If the system can drive to 17, then the circuitry is fine and it’s more than likely connections at the source, a dirty source, or filaments that need to be replaced.

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