[sdiy] Microphonics

Tim Ressel timr at circuitabbey.com
Mon Jan 22 22:39:07 CET 2018


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 
> <mailto: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 <mailto:timr at circuitabbey.com>
>
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-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com

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