Teardown, Analysis and Repair of an Agilent E4407B 26.5GHz ESA-E Spectrum Analyzer

In this episode Shahriar takes a detailed look at an Agilent (Keysight) E4407B ESA-E Spectrum Analyzer. The instruments reports an “Unlock LO” error message which prevents internal alignments from being performed. Before the repair process can begin, the firmware of the instrument must be updated. The firmware upgrade requires the installation of additional flash memory ICs which is presented in the video. The main processor board with its various components are also described in the video.

The complete block diagram of the spectrum analyzer is presented with a detailed look at the principle of operation of the instrument. All the main functional blocks such as the YIG Oscillator, Phase Detector, LO Path, LO Amplifier, Charge Pump, Pre-tune segments, digital circuits, IF and LO paths are analyzed both in schematic and on the PCB. Several potential faults are investigated and measured.


  1. Michael says:

    Would love to know where you got the schematics. The video length and depth of your troubleshooting was appreciated. Thanks.

  2. Alejandro Navarro says:

    Hi Guys,

    Do you know where can I buy the Part (Mixer) for the E4407B?
    Any companie that sells part od Agilent discontinued product?



  3. asghar dabiri says:

    1. I want to know how the data after alignment all will be stored?
    2. How can I buy schematic diagram for E4407?

  4. Paul says:

    Man your videos are the absolute best to be found on the net. As an electrical engineer (not RF though) there’re still many things to learn in every episode. Thank you so much for all the effort and keep the good work up!

  5. Dave says:

    Bravo. Terrific video. Don;t be concerned about the length. It’s all about the content. Someday you can share some of your secrets about finding equipment that are good candidates for repair.

  6. Peter says:

    Whoooaa what an awsome video. It’s so nice to see you figuring things out as you go along. Don’t hesitate to publish videos of this type and length.

    Regards, Peter

  7. Kirk says:

    I loved this video! A great way to learn microwave RF is to study some of the best test equipment on the market. The long length was fine — that’s what it takes to present the material.

  8. Jasper says:

    Watched it all the way. Very interesting stuff! I don’t mind all the details your are going trough. Keep up the good work.

  9. Windsor Chan says:

    Great job! Better then the watching CSI 🙂 I watched over two sittings. I like the detailed walk through the troubleshooting process.

  10. Ejaz says:

    Please attach your twitter account with Facebook. Thanks for all the effort man. Keep it up.

  11. Kelvin says:

    Thanks for the 2-hour video. I do enjoy video that goes into the technical details, though I have to admit that I do not understand a big part of it. I look forward to you going into each subsystem and explain how they work, e.g. the previous DAC video.

  12. tasweet says:

    hello Shahriar,

    loved the video. love all the videos. two hours is not too long. I’ve seen movies that were that long and no where near as entertaining. i enjoyed your thought process and noticed that you have an advantage in that you have more tools and of course you know what is going on.

    keep making videos.

    oh yeah, i do not like to sit thru 2 hour movies.

  13. Richard says:

    I enjoyed your video – but I had to watch it in several segments :). I can’t say I fully understood what the instrument is good for (hopefully you will show how to use it in future segments) but what I got out of the video was the process of how to read a block diagram to find where a problem might be – and the importance of sticking with the repair job even when faced with ordering an expensive special part when you aren’t 100% certain that is the problem.

  14. Paul Rautenbach says:

    I watched the whole video – I like long videos with technical content. I followed the gist of most of it I think.
    I’m trying to learn a bit about electronics of various types. Gradually, I am soaking up more and more.

    I like the clarity of your explanations. Thanks for taking the time do do these videos. The effort put into them is appreciated.


  15. matin z says:

    Shahriar, Thank you for this ENORMOUS repair video 😀

  16. Christian says:

    Watched to the end – amazing bit of fault finding and fixing on a very complex instrument – well done Shahriar!

  17. John Dekker says:

    Great video. I loved the detail you provided. You just don’t get that anywhere else. Great result.

  18. Bill Watt says:

    This was a very valuable learning session for me. Its great to see your thought process and the way you improvise testing techniques to follow the signal path. Thank you very much!

  19. Tristan says:

    Hi Shahriar,

    thanks for the video. Interesting as always and very much educating. Please, if you don’t mind talking about the details, then do so! They are the reason why I like your videos that much! In my opinion, a lot of value is lost if the presentation is cut short just to fit in a certain time frame. Watching your videos takes some time, and I think there is absolutely nothing wrong with that.

    To answer the question from the video, the different slopes seen on the scope when measuring the control voltage of the YIG oscillator (and thus, the control current after all) would be related to the subharmonic mixer. To keep the resulting sweep speed constant, it must be slowed down by the factor of the harmonic frequency used for the conversion in the mixer.

    Keep up the good work!

  20. Roberto Barrios says:

    Hi Shahriar!

    Very interesting and useful! I did not want it to end, I wanted it to last 8 hours (I still do).

    I have some nasty words for you (all of them out of plain envy) but I’ll keep them for myself 🙂

    It would be great to have more frequent videos but given the content, I can only thank you for what you do.

    Keep up with it!

    Thank you,

  21. David says:

    Awesome job! Loved watching it. The video is good balance between theoretical background and practical repair. The explanations on the block diagram/schematic before you head over to the board makes it much easier to follow you, at least for me. I would have loved to see some footage of the firmware upgrade, like you did it with the soldering job. I also liked the fact that you put it all together in one video, so it is possible to stay on target even if you have to order parts and so on.

    Looking forward to your next video!

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