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DDS-60 kit problems

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  • John Parkins
    Hello All, I ve just built a DDS-60 kit with the idea of linking with my v6 board but I m having a few problems with it. The builders notes say there should be
    Message 1 of 3 , Aug 1 12:23 AM
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      Hello All,

      I've just built a DDS-60 kit with the idea of linking with my v6 board
      but I'm having a few problems with it.

      The builders notes say there should be 5v p-p at the output of U4,
      well I only have just under 1v p-p. Is this enough to drive the
      AD5851? It wouldn't seem so as I have no output from the chip.

      It also only draws 50mA most of the time with none of the chips
      getting hot, I know they do run hot. Every now and then though it will
      suddenly draw about 150mA and the chips do get hot but I still don't
      have an output.

      Unless the oscillator module is bad I can't see a problem with that,
      after all it's just one chip and a cap, the supply voltage is correct.

      I've checked all the solder joints under a microscope and looked for
      bridges but I can't find anything wrong. Is it just a bad oscillator
      module giving low output?



      --
      Best regards,
      John mailto:kvp@...
    • n3hkn
      I had a somewhat similar problem but with a PIC-El driving the DDS- 60. Upon start-up a bogus frequency function word seemed to be generated at times and I had
      Message 2 of 3 , Aug 1 4:54 AM
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        I had a somewhat similar problem but with a PIC-El driving the DDS-
        60. Upon start-up a bogus frequency function word seemed to be
        generated at times and I had to reset the PIC software. Maybe you are
        giving the DDS a function word that it cannot act upon.

        Dick N3HKN

        PS: I found that spurious "stuff" made the DDS-60 unusable with my V6
        and V5. It works but signals in the 2 to 7 db above noise range
        competed with the spurs.


        --- In softrock40@yahoogroups.com, John Parkins <john@...> wrote:
        >
        > Hello All,
        >
        > I've just built a DDS-60 kit with the idea of linking with my v6
        board
        > but I'm having a few problems with it.
        >
        > The builders notes say there should be 5v p-p at the output of U4,
        > well I only have just under 1v p-p. Is this enough to drive the
        > AD5851? It wouldn't seem so as I have no output from the chip.
        >
        > It also only draws 50mA most of the time with none of the chips
        > getting hot, I know they do run hot. Every now and then though it
        will
        > suddenly draw about 150mA and the chips do get hot but I still don't
        > have an output.
        >
        > Unless the oscillator module is bad I can't see a problem with that,
        > after all it's just one chip and a cap, the supply voltage is
        correct.
        >
        > I've checked all the solder joints under a microscope and looked for
        > bridges but I can't find anything wrong. Is it just a bad oscillator
        > module giving low output?
        >
        >
        >
        > --
        > Best regards,
        > John mailto:kvp@...
        >
      • zs6buj
        Hi John The AD9851 remains cold if it does not get the 30 MHz reference oscillator signal, and also if the control word is invalid. When it is running
        Message 3 of 3 , Aug 1 10:55 PM
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          Hi John

          The AD9851 remains cold if it does not get the 30 MHz reference
          oscillator signal, and also if the control word is invalid. When it
          is running properly, it dissipates more than 500 mW and gets quite
          hot.

          So I would check to see if you have the reference signal, and make
          sure the code word is good. Then check to see if you have rf out of
          pin 21. Finally, check to see if the AD8008 is amplifying the output
          signal. I'm only getting about 2.5 v p-p out, but it's easily enough
          to drive SRv6.

          My DDS-60 produces a resonably clean signal, but does have one or two
          small spurs. Neverthless, it's quite usable, and you can always shift
          frequency slightly. It is important to ensure the output looks into a
          resistive 50 ohm load, otherwise the signal quality is compromised.

          Good luck
          73
          Eric
          ZS6BUJ


          --- In softrock40@yahoogroups.com, "n3hkn" <n3hkn@...> wrote:
          >
          > I had a somewhat similar problem but with a PIC-El driving the DDS-
          > 60. Upon start-up a bogus frequency function word seemed to be
          > generated at times and I had to reset the PIC software. Maybe you
          are
          > giving the DDS a function word that it cannot act upon.
          >
          > Dick N3HKN
          >
          > PS: I found that spurious "stuff" made the DDS-60 unusable with my
          V6
          > and V5. It works but signals in the 2 to 7 db above noise range
          > competed with the spurs.
          >
          >
          > --- In softrock40@yahoogroups.com, John Parkins <john@> wrote:
          > >
          > > Hello All,
          > >
          > > I've just built a DDS-60 kit with the idea of linking with my v6
          > board
          > > but I'm having a few problems with it.
          > >
          > > The builders notes say there should be 5v p-p at the output of U4,
          > > well I only have just under 1v p-p. Is this enough to drive the
          > > AD5851? It wouldn't seem so as I have no output from the chip.
          > >
          > > It also only draws 50mA most of the time with none of the chips
          > > getting hot, I know they do run hot. Every now and then though it
          > will
          > > suddenly draw about 150mA and the chips do get hot but I still
          don't
          > > have an output.
          > >
          > > Unless the oscillator module is bad I can't see a problem with
          that,
          > > after all it's just one chip and a cap, the supply voltage is
          > correct.
          > >
          > > I've checked all the solder joints under a microscope and looked
          for
          > > bridges but I can't find anything wrong. Is it just a bad
          oscillator
          > > module giving low output?
          > >
          > >
          > >
          > > --
          > > Best regards,
          > > John mailto:kvp@
          > >
          >
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