Squealing switching power supply

[Max Moor]

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,

Max

 

[sofie]

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.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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"Max Moor" <maxmoor@remove_hotmail.com> wrote in message
news:Xns94DCDDE21C76Dmaxmoorhotmailcom@199.45.49.11...

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,

Max