Optimize Quad Frequency on 5977 source

Hi, Post

The 5973 and 5975 manuals had the recommended range to adjust the quad frequency when  entering100mz and 650mz, but I don't see the recommended ranges in the 5977 manual under adjusting the quadrupole frequency. What are the recommended values for the 5977 MS?


  • There is rarely a reason to optimize the quad frequency.  It's only needed to be done when replacing electronics or if the system has high drive due to adhered sample residue deposits that are changing the quadrupole and quad drive subsystem's total capacitance.  If the quad cannot stay on, cannot be adjusted, at the high setting, the probable fix for that is analyzer replacement along with remedial cleaning of the manifold to remove the residue deposited there so that the clean analyzer is not contaminated by the stuff already inside the vacuum chamber.

    The 5977 Series Troubleshooting and Maintenance Manual pages 134/135, 5977B version pages134/135, and the 5977C version pages 132/133... all say 100 and 650.

  • The 5977 manual only says to enter 100 and then 650. It does not give the typical minimum voltage. 

    For example the 5973 manual (pg. 239) says for 650 amu "the minimum voltage is typically between 500 and 650 mV"

    The 59675 (pg. 145) says for 100 amu "The minimum voltage is typically between 50 and 70 mV"

    We had the boards replaced recently and I wanted to confirm the values are still in the typical range.

  • At 100 it's typically below 100mV.  At 650 it's typically below 750mV.   

    The raw number changes as the quad heats up during the test from the applied voltages. The raw number is not absolute, don't think that "it should be 66mV but I can only get it to minimize at 68mV" -- that is not meaningful. This adjustment needs to be close but a tiny amount of a turn off either way won't cause any difficulties. Make sure that both adjustment slugs are out about the same distance - don't have one adjusted way in and one adjusted way out, for example.

    This is not adjusting the frequency, this is minimizing the required power needed to drive the quad RF at two different setpoints. Lower power is better for the electronics and the quad itself, better for the lifetime of the instrument, and only sort of tells you if the electronics and quad subsystem are functioning properly. If a system can't be dipped it means more troubleshooting but if it can be dipped and the minimum is below the aforementioned limits above, run it.

  • Thank you so much. Our numbers are 53mV at 100 amu and 320mV at 650 amu so I will leave it and run as is.

  • Great!  How many runs on your system?  It's interesting to know and tells something about the total amount of deposited sample residue inside the MS.

    From the GC front panel:

    • 8890 and Intuvo: Service Mode, Instrument, Usage
    • 7890: Service Mode, Diagnostics , Instrument Status
    • 6890: Options, Diagnostics, Instrument Status
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