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Switching PSU audible noise

Discussion in 'Electronic Repair' started by System Alchemist, Sep 19, 2005.

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  1. 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!
     
  2. Pooh Bear

    Pooh Bear Guest

    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
     
  3. I read in sci.electronics.design that System Alchemist
    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.
     
  4. Dave D

    Dave D Guest

    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
     
  5. Ian Phillips

    Ian Phillips Guest

    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
     
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