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    <p>Yes, it tracks vco frequency. No switchers. Power draw is low so
      I don't think its the big electros. <br>
    </p>
    <p>btw microphonics can go both ways. It is caused by the dielectric
      being piezoelectric, and that can both generate and absorb sound.</p>
    <p>--tr<br>
    </p>
    <br>
    <div class="moz-cite-prefix">On 1/22/2018 11:31 AM, Roman wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:1849fec8d39a42a3bf7d5b5512f112c9@grupawp.pl">Is whining
      somehow related to VCO frequency?<br>
      Do you have any DC/DC converter?<br>
      My first guess would be the largest ceramic cap you have there.<br>
      Or electrolytic capacitor run over maximum ripple specs.<br>
      <br>
      Roman<br>
      <div><br>
      </div>
      <div class="nh_extra">
        <p>Dnia 22 stycznia 2018 17:24 Tim Ressel <<a
            href="mailto:timr@circuitabbey.com" moz-do-not-send="true">timr@circuitabbey.com</a>>
          napisał(a):<br>
        </p>
        <blockquote class="nh_quote" style="border-left: 2px solid #999;
          padding-left: 8px; margin: 0;">
          <div id="gwp3b3c4a3d">
            <div>Got a weird one...<br>
            </div>
            <div><br>
            </div>
            <div>An oscillator I designed is whining. Well, some units
              do it. It is faint<br>
            </div>
            <div>and you have to have your ear right up against the
              board to hear it. But<br>
            </div>
            <div>an end user complained so we had to investigate. Other
              weirdness ensued<br>
            </div>
            <div>but we got the customer taken care of.<br>
            </div>
            <div><br>
            </div>
            <div>My question is: how to find where the whine is coming
              from? I tried<br>
            </div>
            <div>using a microphone but could not pick anything up. This
              is an ASM-1 type<br>
            </div>
            <div>VCO (saw core) so there is a pulse train present. That
              could explain the<br>
            </div>
            <div>mic not picking it up. I tried putting my finger over
              various components<br>
            </div>
            <div>on the board with no luck. I thought about using an
              accelerometer but it<br>
            </div>
            <div>would have to be high sensitivity and low mass to work.<br>
            </div>
            <div><br>
            </div>
            <div>I am at a loss.  Any thoughts?<br>
            </div>
            <div><br>
            </div>
            <div>--<br>
            </div>
            <div>--Tim Ressel<br>
            </div>
            <div>Circuit Abbey<br>
            </div>
            <div><a nh-compose-link=""
                href="mailto:timr@circuitabbey.com"
                moz-do-not-send="true">timr@circuitabbey.com</a><br>
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    </blockquote>
    <br>
    <pre class="moz-signature" cols="72">-- 
--Tim Ressel
Circuit Abbey
<a class="moz-txt-link-abbreviated" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a></pre>
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