Re: [very very OT] noisy power supply
Here's my take on fans and dust and noise.
Having fans inside a computer case (such as those mounted on the CPU's
heat sink) lower the air pressure inside the case - Bernoulli's principle.
Having a fan blowing out further decreases the internal pressure.
Nature hates this pressure difference and therefore air IS going to infiltrate
into the case. Unfortunately, it's going to get in someway, somehow - like
floppy drive slot, cd-rom door, places where the case doesn't fit real tight,
etc.
The problem with this scenario is that those places are relatively small and
therefore the air is going to move fast through those slots. Fast air carries
dust and dirt and hair and etc. Once inside the case that air is going to slow
down and loose it's ability to carry that junk. Buildup on the floppy drive,
the lens of the CD-ROM's laser and other areas is likely to occur.
Fortunately, there is a solution. Turn the fan around like Joerg has
suggested. This will make the case positively pressured and will keep
air (and junk) from infiltrating those nooks and crannies. However,
Sebastiaan is right - the dirt, dust, hair junk issue is still going to be
a problem. The solution to THAT problem is to put a filter in front of
the fan.
My wife owns a Veterinarian Hospital. These places are VERY dusty.
LOTS of hair and dander and dirt in the air. We'd have MAJOR problems
if the computer system wasn't designed right. The case I chose for her
system (running Debian GNU/Linux of course...) has a HUGE fan in the
front (it's a rack mount case, BTW) with a two stage filter. As long as
the filters are cleaned routinely there is no accumulation inside the case.
We also have very low incidences (like 0) of problems with the LS-120,
QIC or CD-ROM drives. The system has been up and running for nearly 5 1/2
years without problems, so I'd say it works.
As for noise, get the quietest fans possible - ones with ball bearings seem
to be better than those that use brass bushings or sleeves. Variable speed
would obviously help - especially if the fan is oversized so it doesn't have
to run full tilt. Also, make sure that the case has enough places for the
forced air to escape - too few and the fan will have to work harder - harder
equals louder. However, too many slots would/could negate the benefits
of trying to positively pressurize the case. I remember the Original IBM AT's
that ran cooler if you taped over some of the air holes in the front of the
case...
The only other thing to make the noise less of an issue is to put something
between you and the noise source. Having the computer under your desk,
in an enclosure, in another room all have worked for me... :)
Chuck
Sebastiaan wrote:
> On Wed, 11 Jul 2001, Joerg Johannes wrote:
>
> > Hi list
> >
> > My power supply takes warm air from inside the PC case to cool itself.
> > As Athlon processors (especially >1000 MHz) tend to produce lots of
> > heat, the temperature-sensitive power supply fans turn faster and
> > faster, making lots of noise. (When I start the box, I don't hear it at
> > all, but 10 minutes later, I wish back to my old one...)
> > So my idea is: I open the power supply, flip the fan so that it blows
> > cool air from outside into the case, voila, much less noise. Is this a
> > good idea or rather stupid?
> >
> Hello,
>
> thats stupid and dangerous. Dust is pulled into the computer. I had once a
> big fan on my computer case blowing air inside. Six months later I noticed
> (by accident) that my cpu fan rotated very slowly. It was covered with
> dust, so my cpu could be overheathed soon.
>
> But a powersupply should be handled with even more care: dust is flamable.
>
> My advice: look for a silent fan or a silent power supply. Be aware that
> the power supply is the only component in the computer with high voltage
> and therefore it could be dangerous if something went wrong.
>
> I learned that the best way to make your computer silent is to put it into
> another room. Even the lownoise of the cpu fan becomes irritating.
>
> Greetz,
> Sebastiaan
>
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