Teardown and Repair of an Agilent E4433B ESG-D Synthesized Signal Generator (December 2014)

In this episode Shahriar repairs an Agilent E4433B ESG-D Synthesized Signal Generator. This 4GHz unit shows the “UNLEVEL” error for all frequencies and at all output power levels. After a close look at the system block diagram the fault is traced to the main Output RF board.

The Output RF board is equipped with various amplifiers, electronic attenuators, I/Q mixers, heterodyne paths and final PA. By using soldered SMA cables to various points in the signal path, the fault is traced to an internal amplifier chain which is likely made of a MESFET or JFET transistor. Since this part is obsolete, an RFMD GaAs hybrid amplifier is used in its place. The biasing network and matching networks need to be modified to accommodate this change. The repaired unit is then verified for functionality and performance by measuring a QAM constellation output signal.


  1. Ron Purcell says:

    My E4433B has a different problem, namely an output level error that switches back and forth between +5 and +10dB as level is increased up to +3dBm, above which the error stays constant at +5dB. Presumably this is some kind of DAC problem affecting both the mechanical and electronic attenuator. If anyone has fixed this kind of problem I’d appreciate feedback. Thanks!

  2. AJ says:

    Hello my friend very informative.
    Can you tell me where I can get a block diagram of the HP4433B I looked everywhere. Or perhaps you can send me a PDF copy of yours?

    Thank you,


  3. Paul says:

    I have one of these that is showing the same fault. but where is this faulty component?

  4. Luke Smith says:

    I don’t know anything about RF amplifiers, and what they do, so this video was very helpful. I always learn better by doing things, or ever seeing how it is done, so the video where he points to the blueprints was very nice. It looks very complicated, so I finding someone that has the knowledge to fix this equipment is a great help. http://www.medsystech.com/services.html

  5. stefan says:

    Thank you very much for your great video. I have a E4432B with the same faulty transistor. The NBB-310 you were using is not available anymore. so I thought of using a MACOM MAAM-009560. It is only 250MHz to 4GHz but has better linearity and less noise.

    Please tell me what you think about this amplifier as a replacement.

    Thanks again. Stefan

    • Steven says:

      Hey Stefan,

      Did you have success with the MAAM? If so, would you mind sharing your results and schematic?



  6. Robert says:

    Great video and very informative. Thanks for the insight

  7. S Wood says:

    Thanks for the video on repairing this signal generator. I love the step-by-step explanation of the troubleshooting thought process. Congratulations on getting it working (without a schematic).

    I give it a thumbs up!


  8. Jim popwell says:

    Loved the two hour repair, I thought it was the op amp. Have one main suggestion. I enjoy your excitement very much but please talk slower . I know about plls and analyZers. But even then your hard to follow just because of your speed. I love the teaching you do. Your very good. Keep me updated Thanks again. Jim

  9. Hassan says:

    Really top notch work, especially considering the references you had (or didn’t have) available.
    One thing, that maybe be interesting (really more of a curiosity) is to back down modulated power and measure the EVM floor.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

  • Social Media

  • Administrator

  • Archives

This site is protected by Comment SPAM Wiper.