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  • EEVblog #540 – HP35670A DSA Repair – Part 3

    Posted on October 27th, 2013 EEVblog 10 comments


    More progress (or is it?) on the HP35670A DSA repair.
    Part 2 HERE
    Part 1 HERE
    Forum HERE

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    • Sam Reaves

      Dave,

      You might drop a note on the HP/Agilent group on Yahoo! Groups and ask if someone might have a CLIP (Component Level Information and Parts (I think)) on the HP35670A DSA. You might luck out a lot of HP old timere hang out there. The other place might be http://www.hparchive.com. Mostly older instruments there but it never hurts to ask.

      Sam

      • http://www.eevblog.com EEVblog

        Thanks. Various people are looking into this for me, but so far no luck.

    • Johm

      What about isolating the positive and negative rails from the analog board and powering all the analog ICs and circuitry with the lab’s supply? Then you could see which ones are working fine or not. And then find out if it’s a passive or any Op Amp.

      • f4eru

        If you still have acess to a FLIR camera, it may help to identify the ICs that draw more power :))

        • http://www.eevblog.com EEVblog

          I have a FLIR camera on the way! Need the extender card first though.

    • Chris

      You know, it really does look like the “Half” light comes on when you touch that BNC connector (11:35-ish).

      Anyhow, I am really liking this series. Learning a lot by watching you figure your way through it. I do hope you can find the schematic and get the thing figured out. I have an older Onkyo stereo that I have tried to fix, but I have the schematic for it. I just don’t have all your experience and skill :).

    • Worf

      If the ADC’s output is that crappy, it’s obviously the opamp following it that’s faulty – ADCs aren’t known for their huge source/sink capability and are almost always followed by a buffer/amplifier stage to increase drive capability. I’d look at the opamp immediately following the output (just take it out as loading down the ADC enough to output garbage.

    • Marcin

      If there are various voltage power supplies in addition extreme, probably burned IC OP AMP, DAC, ADC, and probably something else.
      Repair is just unlikely (cost …!).
      Good to have a schematic for a while to assess how a particular block.
      It is not always able to easily fix it.

    • Kevin

      Dave,

      I really hope you continue to work on this thing. This is where many people, mainly me, get stuck. I can fix the obvious problems and perhaps a few others but if that doesn’t do it I am sometimes at a loss on what to do next. I know it is probably not worth the time to fix it but the education it would provide would be valuable. Can you show us an easy way to check some of those suspect IC’s? And more of your thought process on other things you suspect.

      Thanks
      Kevin

    • Rami

      Hello Dave,

      First, your blogs are great! Thank you very much for your work, I am always anxiously waiting for your next post and I am learning a lot.

      Second, please don’t give up on this repair, I am itching to see the DSA diagnosed.

      Thank you again and good luck!

      Rami