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Squealing switching power supply

Discussion in 'Electronic Repair' started by Max Moor, May 2, 2004.

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  1. Max Moor

    Max Moor Guest

    Hi All,
    I bought a junker VCR. It seems to work fine, but has a squealing
    switching powers supply. I know the supply isn't worth replacing, but I'll
    bet I have, or have access to, most of its parts.

    I remember old rules-of-thumb like, if you hear a 60 cycle hum on an
    old radio, the filter caps on the power supplay are probably bad. Are
    there any rules-of-thumb like this for squealing power supplies? I have a
    scope, but don't even really know where to probe.

    Thanks for any thoughts,

  2. sofie

    sofie Guest

    Max Moor:
    Usually the culprit in a "squealing" switch mode power supply is a shorted
    or excessively heavy load but since you stated that the VCR seems to work
    fine I would then suggest that there are one or usually many electrolytics
    that have become faulty and will measure high ESR. If you do not have an
    ESR meter to check them, just replace all of the electrolytics in the power
    supply, usually not an expensive task and in fact many suppliers will sell a
    rebuild kit for many of the more popular power supplies.
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