Electronics > Projects, Designs, and Technical Stuff

"singing" board (audible noise), how to pinpoint?

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Ice-Tea:

--- Quote from: Siwastaja on February 21, 2020, 06:44:55 pm ---Or, use a toothpick or similar to touch/press components one by one, likely a small amount of compression makes the sound stop, helping you pinpoint the suspect.

--- End quote ---

^^This.

Psi:
Could also try a ~5khz disc piezo with a toothpick or wire glued to it.
Hold the thing with some foam to let it vibrate freely.
Then touch the toothpick to various parts while watching Oscope.

if that doesn't work, you could try generating a beat frequency.
Pick a source frequency that, when mixed with the 5hz noise, will generate a unique beat frequency
Feed that frequency into the piezo then go around touching parts and listening for the new sound.

Psi:
Could also try doing an overclock/underclock on the CPU and other peripheral clocks
See what, if any, affects the sound frequency.
Might tell you something.

SiliconWizard:

--- Quote from: roland on February 21, 2020, 05:43:52 pm ---I know the usual suspects, we have checked all inductors and MLCCs near the power supply, DC-DC converters (power companion chip) etc., however we didn't find anything yet that might correspond even remotely to the 5kHz we're seeing (or better, hearing).

--- End quote ---

How did you proceed then? Because yes those definitely look like the usual suspects.

Ceramic capacitors when this happens will transmit vibrations to the PCB and it's sometimes hard to locate the source precisely (until of course you shut it down).

RoGeorge:
Take a wooden or a plastic rod, and use it like a soundwaves guide.

Touch one head of the rod to the ear cartilage, and the other head of the rod to various parts on the PCB.  You'll be surprised how effective this could be.  If too loud, use the head bone from outside of the back of the ear.

First suspects will be the coils with magnetics (e.g. SMPS coils).  MLCC capacitors might sing, too.

What tune is it singing, tho'?   ;D

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