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HP 8640B - Need Help!

Discussion in 'Electronic Equipment' started by Andrea, Aug 23, 2003.

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  1. Andrea

    Andrea Guest


    A few days ago I became a (almost 100%) happy owner of a HP 8640B with
    Options 001, 002 and 003. Unfortunately, this fine piece of equipment
    suffered a subtle freight damage and demonstrated ZERO RF output when
    checked. After some hours of work, I traced the fault to a Hybrid HP
    Amplifier in the AM modulator, of which I've a photo:

    By shorting input and output of this IC I've been able to see a signal
    at the output, although with reduced power and some distortion,
    courtesy of the impedance mismatch. Unfortunately, all my attempts in
    trying to find a replacement have been unsuccessful so far. Can anyone
    point me in the right direction? All other functions seem to work just
    fine, and the generator itself is in good shape and really worth the
    effort to bring it back to life.


    ICQ #15014472
    remove NOSPAM to e-mail me
  2. Robert Baer

    Robert Baer Guest

    I assume you checked with HP,and that they want a fortune for it....
    If you have a good idea as to exactly what each pin is for, as well as
    the function, input and output specs, maybe you can make a small
    breadboard replacement?
  3. Andrea

    Andrea Guest

    Not exactly. I went through some refurbished test equipment dealers
    that I know of. Never thought of HP in the first istance because of
    their "10-years support and then you are on your own" policy. But it
    might be worth a try, in fact. Actually, I'm not making a big problem
    out of spending a fortune of it, as it's an expense which is going
    into the insurance claim anyway.
    Nope. Not for a ultra-linear amplifier from 450 KHz to 550 MHz. I
    doubt I could ever reproduce the gain, linearity and noise figure
    that HP was able to put in. Unless I want to part with the excellent
    performances of this generator, which is something I don't even


    ICQ #15014472
    remove NOSPAM to e-mail me
  4. Fred Abse

    Fred Abse Guest

    The 8640B is one of the lowest noise signal generators ever made. I
    rather suspect that's what Robert had in mind when he got it.

    If you're going to use it for testing links, it matters.
  5. Fred Abse

    Fred Abse Guest

    Sorry 'bout that. I just looked back up the headers for the name, and the
    OP had scrolled up out of sight.

    Must get new glasses.

    I promise it won't happen again, honest :)
  6. Robert Baer

    Robert Baer Guest

    There are a *lot* of op-amps that have bandwidths that exceed 550Mhz,
    so with feedback or gain strapping options - depending on design, one
    would be able to have an amp 0-550MHz with (i think) reasonably
    comparable noise figure.
    Then one would have to add a bandpass filter - say a passive one in
    the input.
  7. Well, check out this ebay auction anyway
  8. Phil J

    Phil J Guest

    Try Fair Radio Sales at
    that's where I got mine.
    Phil J
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