Teardown, Repair & Experiments with the Anritsu 37347A 20GHz Vector Network Analyzer

In this episode Shahriar repairs an Anritsu 37347A 20GHz Two-Port Network Analyzer. The unit does not boot up and as a result its internal state is unknown. The boot fault is traced to a bad RTC module which has a built-in integrated battery. A replacement unit is located which allows the unit to fully boot.

The instrument initially displays an unlock condition on the internal PLL. This problem is resolved by loading the PLL calibration files from the HDD. The complete block diagram of the unit is examined in detail and an unusual PLL intermittent locking problems is demonstrated. Various measurements on several of the internal PLLs confirm their functionality. As a final experiments, the instrument is calibrated and the S-parameters of a tune-able band-pass filter is measured.


  1. Claire Bérubé says:

    information sure vos Produit et Entreprise tel:(418) 873-3003

  2. Holmes kuan says:

    Very nice video, it real helps a lot.

    But My 37369A always display “6024 phs lck fail DE” after I replaced the Timekeeper, and BT1.

    As you mentioned, you fixed the YIG osc lookup table, could you please explain it more detailed?

    • Philip Davies says:

      Hi Holmes

      I have a simular situation as your Anritsu Network Analyser, but my Hard Drive removed by a computer company thinking its private data on it when its only the opperating software on it !, all the data lost, which I presume your hard disk is ok? because it may contain the look up calibration tables on it?
      As your unit both the Timekeeper IC in my unit (37225A) IC by ST, M48T08-150PC1 and Rayovac Lithium Carbon-monofluoride Battery type FB1225H2 battery are flat all needs replacement, so I looked it up the info on the internet as I am in a worse situation as yourself due to no hard drive to obtain any stored calibration data,
      F.Y.I have a look at section 6-6 page 86, PDF version of Wiltron – Anritsu 373XXA sort of service – calibration manual? no real drawing will ever be supplied from Anritsu not in the UK anyway, 🙁 I wish they were would make life easy for anybody who wishes to keep the units running, this is a hobby for me getting the old test equipment working again :), big heavy item for sure !, but built well,


      Drive your frequency counter external reference from a external 10MHz disiplined oscillator – GPS frequency standard, and set up for best accuracy of frequency, follow instructions in manual supplied,

      Best of luck to you Holmes

      from Cheshire England UK
      Anybody wishes to part with anritsu analyser let me know, I am also looking for Anritsu 3.5″ floppy disks that were supplied with the unit

  3. Bobby says:

    Great video, as always. The most informative part for me as a beginner in the HF field was actually the block diagram you went through. Your process of debugging is also very interesting, and the more of your thoughts you are able to communicate as you go through the repair steps, the more I enjoy your repair videos.

  4. Mitch says:

    Haven’t seen any new posts in a while, Shahriar. I hope all is well with you, and that you’re enjoying some personal time (as opposed to crazy busy at work). But please know that your videos are very much appreciated, anticipated, and enjoyed by so many of us. But you are missed!

  5. azim says:

    Hi Dear
    I had repaired two of this series 40Ghz
    It was very hard because there was no documents

  6. George Robinson says:


    Nice video but I’d like to see how you use the VNA – not only how you repair it.

    For example how to measure the characteristic impedance of an unknown coax with it, how to calibrate it using the SOLT method and other methods + what are the differences between them. What are the common traps of using a VNA.

    You did similar videos about scalar spectrum analyzers, but I don’t recall you taking about the difference between them and VNAs from the operator’s point of view.

    …and maybe somebody could finally explain why the S12 parameter does not refer to the transmission from Port1 to Port2, but vice versa! 😮

  7. JF says:

    awesome video! thanks for putting this again!

  8. John Wallace says:

    Another great video – many thanks once again.

    Particularly amusing for us old guys to watch someone discover the mysteries of a MVME based piece of hardware and its software “features” – namely the need to set the clock before anything will work – a useful reminder to those who were cynical about the significance of the Y2000 bug!!

    • Staffan says:


      Would you by any chance have some more info regarding the MVME? It seems like quite a few VNAs have been bricked by a dead battery backed RAM. Any hints on how to get the MVME162 up and running after a dead BBRAM?


  9. terry says:

    i always enjoy the videos you put together. thank you so much. it is generous of you to share your knowledge.

  10. Sam Reaves says:


    I could find room for this on my bench for sure!
    How do you get so lucky so often?


  11. Geoffrey says:

    I always enjoy your videos. It’s a lot of fun to learn how to solve problems and I think you’re doing a great job at communicating how.

  12. 2ndAnonymous says:

    Even though its just outside of my comfort zone i did watch the video fully, including the block diagram part. I’m also interested in a repair of the PLL board.
    Thanks for the great videos, all of them.

  13. Anonymous says:

    Thanks for another great video! I would like to see a repair of the PLL board, if you can find the time.

    Can you recommend any good literature where I can read about this stuff like S-parameters?

  14. Vasily says:

    Thanks — great video. Enough depth for me.

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