[sdiy] Microphonics

Roman modular at go2.pl
Mon Jan 22 23:02:42 CET 2018


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.  A photo of the board might bring some ideas also.   Roman   Dnia 22 stycznia 2018 22:44 Tim Ressel <timr at circuitabbey.com> napisał(a):  Yes, it tracks vco frequency. No switchers. Power draw is low so
      I don't think its the big electros.   btw microphonics can go both ways. It is caused by the dielectric
      being piezoelectric, and that can both generate and absorb sound.  --tr   On 1/22/2018 11:31 AM, Roman wrote:  Is whining
      somehow related to VCO frequency?   Do you have any DC/DC converter?   My first guess would be the largest ceramic cap you have there.   Or electrolytic capacitor run over maximum ripple specs.      Roman      Dnia 22 stycznia 2018 17:24 Tim Ressel <   timr at circuitabbey.com >
          napisał(a):  Got a weird one...   An oscillator I designed is whining. Well, some units
              do it. It is faint  and you have to have your ear right up against the
              board to hear it. But  an end user complained so we had to investigate. Other
              weirdness ensued  but we got the customer taken care of.   My question is: how to find where the whine is coming
              from? I tried  using a microphone but could not pick anything up. This
              is an ASM-1 type  VCO (saw core) so there is a pulse train present. That
              could explain the  mic not picking it up. I tried putting my finger over
              various components  on the board with no luck. I thought about using an
              accelerometer but it  would have to be high sensitivity and low mass to work.   I am at a loss.  Any thoughts?   --  --Tim Ressel  Circuit Abbey    timr at circuitabbey.com   ______________________________  Synth-diy mailing list    Synth-diy at synth-diy.org  synth-diy.org synth-diy.org     ______________________________ mailing list
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--Tim Ressel
Circuit Abbey
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