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high pitched noise from computer psu

Discussion in 'Electronic Repair' started by Peter, Nov 7, 2003.

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  1. Peter

    Peter Guest

    ATX computer power supply.
    Rated at 450 watts
    (that's a joke!)
    Made in China.
    works but makes a high pitched noise.
    Must be oscillating somewhere. Most likely cause?
    Faulty transistors? or more likely bad filter caps?
    On input to switching transistors or on the low voltage side?

    I'm looking for tips.
    thanks

    Peter
     
  2. Jerry G.

    Jerry G. Guest

    This can commonly be from the switching driver transformer having some
    internal loose windings, a decoupler cap(s) going defective, or something
    mechanically resonating.

    Most of the time, we found these supplies not worth to invest the time and
    money in to, since they are very low in cost to replace.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    =========================================


    ATX computer power supply.
    Rated at 450 watts
    (that's a joke!)
    Made in China.
    works but makes a high pitched noise.
    Must be oscillating somewhere. Most likely cause?
    Faulty transistors? or more likely bad filter caps?
    On input to switching transistors or on the low voltage side?

    I'm looking for tips.
    thanks

    Peter
     
  3. CJT

    CJT Guest

    They have to oscillate. That's how they work. But they shouldn't
    make audible HF noise. Check for loose screws or laminations on the
    transformer(s).
     
  4. Mike Wilson

    Mike Wilson Guest

    Hi Pete
    I know this might sound a little starnge, but it may be the fan in the power
    suppy. I've had old power supplies that make a high pitched sound. I gave
    them a little thump and the sound goes away. If this problem is the one I
    just described it usually happens with a power supply that is a few years
    old. You mentioned that it is a ATX power supply, the power supply is at the
    top of the case, so if you give the case a little thump, not too hard, then
    it should go away. If what you described isn't the fan, I can't help ya.
    Cheers!!!
     
  5. CJT

    CJT Guest

    It's certainly true that fans can squeal as they reach the end of their
    life, especially the cheap sleeve type. Sometimes they load up with
    dust, too.
     
  6. Bruce

    Bruce Guest

    In Aussie, it would be cheaper to replace the power supply than open the old
    one, maybe upgrade to a P4 then you will need a new PS, but a bit of lube
    spray
    on the fan nver hurt, I've seen PS blow up just because the fan locked up -
    have fun
     
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