[vox-tech] power supply question

[Samuel Merritt]

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On Fri, May 10, 2002 at 05:56:14PM -0700, Peter Jay Salzman wrote:
> power supply fans generally stay on 24/7.  right?
>=20
> i have a power supply fan which turns on for the first second or two of
> powering up, then it comes to a stop (but in such a way that makes it
> look like it wants to turn; it dances a bit).
>=20
> if you leave it on for awhile, it'll start spinning again (with an
> audible click.  sounds like a switch or relay) but only for a few
> minutes.  it'll stop again.  and eventually start up again.
>=20
> when you power the system off, it rotates a few times before coming to a
> halt.
>=20
>=20
> the fan rotates freely when the power is off.
>=20
> any ideas?   (aside from buying a new supply).

Sounds to me like you have a variable-speed fan, probably=20
temperature-controlled, so that it tries to run as slowly as possible=20
while still keeping the power supply cool.

My guess is that the fan's bearings are starting to go out, so when it=20
tries to go at one of its slower speeds, you get the dancing. Then, the=20
power supply heats up, so it goes to a fast speed, and starts running=20
again, cools the supply, and we start the whole cycle over again.=20

You can often replace just the power-supply fan without replacing the old=
=20
supply. They're standard 80mm fans; the only hassle might be cutting the=20
old power leads and soldering new ones on.=20

--=20
Samuel Merritt
PGP key is at http://wwwcsif.cs.ucdavis.edu/~merritt/snmerritt.asc
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