<div>So that narrows it down to capacitors close to VCO core, like timing cap, decoupling caps around reset circuit, or caps around sub-osc divider if you have one there.<br></div><div>A photo of the board might bring some ideas also.<br></div><div><br></div><div>Roman<br></div><div><br></div><div class="nh_extra"><p>Dnia 22 stycznia 2018 22:44 Tim Ressel <timr@circuitabbey.com> napisał(a):<br></p><blockquote class="nh_quote" style="border-left: 2px solid #999; padding-left: 8px; margin: 0;"><div id="gwp90911c5a"><div id="gwp90911c5ah"><div text="#000000" bgcolor="#FFFFFF" class="gwp90911c5ab" data-message-body="true"><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.<br></p><p>--tr<br></p><div><br></div><div class="gwp90911c5a_moz-cite-prefix">On 1/22/2018 11:31 AM, Roman wrote:<br></div><blockquote is-minimized="" type="cite" cite="mid:1849fec8d39a42a3bf7d5b5512f112c9@grupawp.pl"><div>Is whining
somehow related to VCO frequency?<br></div><div> Do you have any DC/DC converter?<br></div><div> My first guess would be the largest ceramic cap you have there.<br></div><div> Or electrolytic capacitor run over maximum ripple specs.<br></div><div> <br></div><div> Roman<br></div><div> <br></div><div><br></div><div class="gwp90911c5a_nh_extra"><p>Dnia 22 stycznia 2018 17:24 Tim Ressel <<a nh-compose-link="" href="mailto:timr@circuitabbey.com" moz-do-not-send="true" target="_blank"></a><a nh-compose-link="" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a>>
napisał(a):<br></p><blockquote is-minimized="" class="gwp90911c5a_nh_quote" style="border-left: 2px solid #999; padding-left: 8px; margin: 0;"><div id="gwp90911c5a_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" target="_blank"></a><a nh-compose-link="" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a><br></div><div><br></div><div>_______________________________________________<br></div><div>Synth-diy mailing list<br></div><div><a nh-compose-link="" href="mailto:Synth-diy@synth-diy.org" moz-do-not-send="true" target="_blank"></a><a nh-compose-link="" href="mailto:Synth-diy@synth-diy.org">Synth-diy@synth-diy.org</a><br></div><div><a href="http://synth-diy.org/mailman/listinfo/synth-diy" moz-do-not-send="true" target="_blank" nh-safe-redirect="" data-saferedirecturl="https://zasobygwp.pl/redirect?sig=b71c8251b717ba551dbce4e296c1ab7f5c1f2f55b0f607f673fe803609e81823&url=aHR0cDovL3N5bnRoLWRpeS5vcmcvbWFpbG1hbi9saXN0aW5mby9zeW50aC1kaXk=&platform=desktop&brand=o2">http://synth-diy.org/mailman/listinfo/synth-diy</a><br></div></div></blockquote></div><div><br></div><div><br></div><div><br></div><pre>_______________________________________________
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<br></pre></blockquote><div><br></div><pre class="gwp90911c5a_moz-signature" cols="72">--
--Tim Ressel
Circuit Abbey
<a class="gwp90911c5a_moz-txt-link-abbreviated" nh-compose-link="" href="mailto:timr@circuitabbey.com" target="_blank"></a><a nh-compose-link="" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a><br></pre></div></div></div><div id="gwpbad79611"><div>_______________________________________________<br></div><div>Synth-diy mailing list<br></div><div><a nh-compose-link="" href="mailto:Synth-diy@synth-diy.org">Synth-diy@synth-diy.org</a><br></div><div><a href="http://synth-diy.org/mailman/listinfo/synth-diy" nh-safe-redirect="" data-saferedirecturl="https://zasobygwp.pl/redirect?sig=b71c8251b717ba551dbce4e296c1ab7f5c1f2f55b0f607f673fe803609e81823&url=aHR0cDovL3N5bnRoLWRpeS5vcmcvbWFpbG1hbi9saXN0aW5mby9zeW50aC1kaXk=&platform=desktop&brand=o2" target="_blank">http://synth-diy.org/mailman/listinfo/synth-diy</a><br></div></div></blockquote></div><div><br></div>