5977A MSD Fault 2 RFPA difficulty

Hi everyone,

Problem with our GCMS (MS 5977A)

If I try to tune or air and water check, nothing happens and I get MSD Fault 2: RFPA Difficulty. 

What I did (after looking in forums)

 - Check the source: i swapped with another source (same model) and the error is still there so it does not seems to be a source problem. (The source works in another system). 

- I changed the EM Horn (it was old anyway)

I saw some discussions about the quad (burns), but even if the instrument is kinda old (almost 10 years) it was not use often and we were careful.. 

Some things I find weirds: 

- Error appear really fast, filament does not even light. I heard a click, nothing happen (filament does not light), error appear and the clicking sound continue until I "accept" the error on the software.

- On the MS Screen, in MS Parameters, I have High Vacuum pressure 1.01e-09 Torr (!!!)

Also, I have MSD Fault Status dec 4 hex 4 on the MS Screen.  

Any idea? Is there a procedure to adjust RFPA?

Thank you

  • RFPA = Radio Frequency Power Amplifier.   The High Vacuum gauge is probably faulty as 10^-9 torr is not achievable.  However, the RFPA error could be thrown with poor vacuum.  Is the high vacuum a turbomolecular pump or a diffusion pump?  How long since the last preventive maintenance was done on the rough pump?  Are you certain the vacuum is good?  

    Fault 2 in your post title is     

    Fault 4 is     

    Help - > Troubleshooting says:

    First is vacuum, then RFPA is not adjusted correctly.   The steps to adjust the Quad Frequency are detailed starting on page 134 of the 5977 Series MSD Troubleshooting and Maintenance Manual.   In general, "dipping the quad" doesn't fix problems, it tells you if the circuitry is functioning correctly.

    And let us know what you find.

  • Thank you. 

    High vacuum is turbomolecular pump. For the rough pump, last oil change was 4 months ago. I check the oil level each week and it is ok, but after closer inspection there seem to be a little be of oil on the pan. So rough pump may have a small leak and probably need a maintenance. 


    I check the vacuum again on the ms screen and I had 7.70e-10 ! 

    When I checked this morning, it was right after I tried to do an air and water check. I tested it again: when I start the air and water check, vacuum drop to e-07 / e-08.. after a couple of minute, I got 3.78e-09... I guess I'll have e-10 after some times..

    Is it normal to change like that ? I guess the clicking sound i hear is the calibrant valve ? Seems like a lot of vacuum variation for just this part ?

    Also, I'm a little lost with the vacuum values: the vacuum on the MS Screen is really different from the tunes reports i had since the installation. If I check my tunes reports, i usually have e-05 / e-06. Big difference between this and e-09 / e-10! 

    If I check with my Agilent GCMSMS (other instrument) right now I have the same value for the tune report, the MS Screen (MS Parameters) and the value on the software (8.46e-05). 

    What is a good vacuum on the GCMS ?

    Thank you for your time, really interesting!

  • Even with no flow and the transferline capped off, the turbo pumps on the 5977A cannot get below 10e-6 torr.  OK, a few may get to the very high 10e-7, but that's doubtful.  10e-10 is either a faulty gauge tube or it's off.  I read about ultra high vacuum pumping and it is very, very difficult to get to 10e-10 on earth.

    Most GCMS single quad systems operate from ~9x10e-6 to  ~4x10e-5 or so with 1.2 ml/min of helium column flow.  GCQQQ systems have 1.2 ml/min column flow plus 7000x systems have 1.5+2.25 collision cell gas and 7010x systems have 1.5+4 collision cell gas so they run in the high 10e-5 range to very low 10e-4.

    Go into manual tune. Do a spectrum scan with the PFTBA valve turned off.  Will it turn on and scan there?  

  • I misunderstood your first reply for the vacuum, my bad! I agree, something is wrong with vacuum reading. 

    I tried the scan with PTFBA closed, nothing happen (same error, almost instantly).

  • The steps to adjust the Quad Frequency are detailed starting on page 134 of the 5977 Series MSD Troubleshooting and Maintenance Manual. 


     In general, "dipping the quad" doesn't fix problems, it tells you if the circuitry is functioning correctly.

  • I cannot reach the setpoints temperature for the source and quad: fault happens after a couple of seconds whatever I do and temperature (source and quad) switch off and drop. Can I still try to adjust the quad frequency ?

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