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!

System Alchemist wrote:

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.

I've heard this problem mentioned in Power Integrations' app notes. See
www.powerint.com

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

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

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.


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.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

"System Alchemist" wrote in message
...
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.


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

"System Alchemist" wrote in message
...
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!


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