Switching PSU audible noise

I have a adsl router (DLink DSL504T) which makes an extremely irritating 10kHz+ whine, this appears to be coming from a

3V3 stepdown switcher's inductor.

I assumed that the noise was due to windings vibrating but trying to damp any movement by squeezing the inductor with my fingers had no effect.

Does anyone have first-hand experience of fixing this kind of issue (I don't really want to redesign the converter!) - RTV or varnish seem like ideas but tend to be a bit final - hence the request for real experience rather than inspired guesses.

TIA!

Reply to
System Alchemist
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I've heard this problem mentioned in Power Integrations' app notes. See

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I've actually experienced more of a 'hissing' in certain cases.

If the transformer's already been varnished you're probably stuck with it.

Graham

Reply to
Pooh Bear

I read in sci.electronics.design that System Alchemist wrote (in ) about 'Switching PSU audible noise', on Mon, 19 Sep 2005:

Wait 10 years and you won't be able to hear 10 kHz any longer. It may be magnetostriction, in which case you need a different coil.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
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Reply to
John Woodgate

It is possible the electrolytic capacitors on the secondary and/or in the regulation circuit are faulty, causing an incorrect load/incorrect switching waveform/frequency, hence the audible whine. They're so cheap, and rather unreliable, I'd try replacing them and see what happens.

Dave

Reply to
Dave D

I think this may be a generic problem with this bit of D-Link equipment.

I bought a DSL-504T a few weeks ago and the whistle is driving me nuts. I don't know what frequency it is, I assume its from the switching supply and I can hear it all round the room. I would put the thing in a padded box but I have needed to see its LEDs several times so its on a shelf noise polluting my environment. BTW I am virtually a senior citizen and its still below my audio cut off frequency.

I bought the modem on line and don't want the hassle of sending it back but I feel that D-Link should have some responsibility here.

Ian Phillips

Reply to
Ian Phillips

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