15 Nov
2006
15 Nov
'06
11:44 p.m.
I'd be surprised if this would turn out to be
singing capacitor.
Every switched-mode voltage regulator needs a an inductor, and
these are much more likely to 'sing'. Probably you have a badly
designed or specified regulator that fails when the load is
below a minimum value (a classic problem with SM regulators).
To test this, load the power supply e.g. via the USB connectors
(a simple USB powered keyboard light could be enough).
If you can locate the component, and it turns out to be an
inductor, applying a bit of epoxy glue on the winding will
probably silence it.
This is an EXCELLENT lead. Thanks Fons.
Can you give me a hint on how to identify an inductor? My notebook case
is open right now and the whine comes from a place out of or near the
CPU. Also, the whine comes when I start Jack at low latencies; I don't
quite understand what the purpose of loading the power supply would be;
I've hooked up my Palm Zire or a USB microphone (which sounded like
crap, but did load the power supply) and experienced no additional hum
whatsoever.
Carlo