<div dir="ltr">Do you have an automotive stethoscope? I would grab one of those and probe around</div><div class="gmail_extra"><br><div class="gmail_quote">On 23 January 2018 at 09:02, Roman <span dir="ltr"><<a href="mailto:modular@go2.pl" target="_blank">modular@go2.pl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><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.<span class="HOEnZb"><font color="#888888"><br></font></span></div><span class="HOEnZb"><font color="#888888"><div><br></div><div>Roman<br></div></font></span><div class="HOEnZb"><div class="h5"><div><br></div><div class="m_2390645076341141776nh_extra"><p>Dnia 22 stycznia 2018 22:44 Tim Ressel <<a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a>> napisał(a):<br></p><blockquote class="m_2390645076341141776nh_quote" style="border-left:2px solid #999;padding-left:8px;margin:0"><div id="m_2390645076341141776gwp90911c5a"><div id="m_2390645076341141776gwp90911c5ah"><div text="#000000" bgcolor="#FFFFFF" class="m_2390645076341141776gwp90911c5ab"><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="m_2390645076341141776gwp90911c5a_moz-cite-prefix">On 1/22/2018 11:31 AM, Roman wrote:<br></div><blockquote type="cite"><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="m_2390645076341141776gwp90911c5a_nh_extra"><p>Dnia 22 stycznia 2018 17:24 Tim Ressel <<a href="mailto:timr@circuitabbey.com" target="_blank"></a><a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a>>
napisał(a):<br></p><blockquote class="m_2390645076341141776gwp90911c5a_nh_quote" style="border-left:2px solid #999;padding-left:8px;margin:0"><div id="m_2390645076341141776gwp90911c5a_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 href="mailto:timr@circuitabbey.com" target="_blank"></a><a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a><br></div><div><br></div><div>______________________________<wbr>_________________<br></div><div>Synth-diy mailing list<br></div><div><a href="mailto:Synth-diy@synth-diy.org" target="_blank"></a><a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a><br></div><div><a href="http://synth-diy.org/mailman/listinfo/synth-diy" target="_blank">http://synth-diy.org/mailman/<wbr>listinfo/synth-diy</a><br></div></div></blockquote></div><div><br></div><div><br></div><div><br></div><pre>______________________________<wbr>_________________
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--Tim Ressel
Circuit Abbey
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