Looking for some help with a 5973 inert MSD that has shifting AMUs.

Since purchasing this instrument used in 2019 we have been experiencing the issue of shifting masses/AMUs. So far the main board, side board and power control board have all been replaced. A new diffusion pump was installed the last time it was serviced in April 2021. We have also installed new columns and electron multipliers. The MSD currently has no issues passing autotune, standard spectra tune of a BFB target tune. Shortly after however the AMUs start to shift by more than 0.1. The higher masses are affected most and will shift so much that peaks are not even present when doing a profile scan in manual tune. This MSD is in tandem with a 6890 GC and is used for volatiles analysis using an EST Evolution concentrator and Centurion autosampler. This issue occurs no matter what filament is in use or the polarity of the detector. We are out of ideas on how to troubleshoot or fix the shifting AMU issue on this MSD. Any ideas or thoughts would be greatly appreciated.

  • Hi

    How is ION Source?

    You did not mention abt it.

    Last when it was being cleaned or changed any parts.

  • Hi,

    The ion source should not be an issue. It has been cleaned throughout this troubleshooting process and was last cleaned 2/1/21 along with changing both filaments. The voltage is only 1259 so the EM should have plenty of life left to it. I did replace the source heater assembly on 3/10/21 with a new one from Agilent because one of the wires was very worn and actually fell off of the assembly. The diffusion pump and power control board were replaced in April and the instrument has been idle since. I like to run a few autotunes every week to see if the masses hold and lately after a few hours they shift more than 0.1 amu.

  • Hi

    Generally, ion source was cleaned but not paying attention on insulator..It should be replaced after sometimes.

    Pls share latest auto tune report to understand better..

    Mass filter is onsite call.

  • If we talked abt GC then column n column ferrule also can generate problem.

    Are there purge n trap also connected with this.

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