More silent PC questions.

I have two PSU I can mod, one is a 250W that has a 92mm side fan (was
blowing into the case), the other is a 300W with an 80mm rear fan that
exausts. When I opened them up, the 300W unit has larger heat sinks, so my
thinking is it will require less air flow to cool it. I like the idea of
the larger fan but the larger heat sinks sound better.

Two ideas I'm playing with, one is a low RPM 80mm "quiet" pull fan installed
in the rear of the PSU. Using a zalman cooler on the CPU (p3-800), try to
get away with passive cooling and let this fan pull the heat out of the
box. There is a small vent just above the PSU that would let some heat from
the CPU escape.

The other idea is mount a 92mm low RPM fan in the lower front and try to
seal up the box so this fan pushes air though the box and out the PSU, with
it's fan removed and the vents enlarged, and also out the rear vent just
above the PSU which is just above the CPU. I could also add a louver over
the CPU area to get some air moving there. This would move more air across
the CPU, have a larger fan which should make less noise and still cool the
PSU.

The use for this box is doing multimedia (slide show/TV tuner) and most of
the time the HD isn't used nor is the system stressed at all, no 3D etc. I
guess I could try both and see, just wondering if anyone has some thoughts
on this.
--

Stacey

On Mon, 12 Apr 2004 00:40:43 -0400, Stacey wrote:

I have two PSU I can mod, one is a 250W that has a 92mm side fan (was
blowing into the case), the other is a 300W with an 80mm rear fan that
exausts. When I opened them up, the 300W unit has larger heat sinks, so my
thinking is it will require less air flow to cool it. I like the idea of
the larger fan but the larger heat sinks sound better.

Two ideas I'm playing with, one is a low RPM 80mm "quiet" pull fan installed
in the rear of the PSU. Using a zalman cooler on the CPU (p3-800), try to
get away with passive cooling and let this fan pull the heat out of the
box. There is a small vent just above the PSU that would let some heat from
the CPU escape.

The other idea is mount a 92mm low RPM fan in the lower front and try to
seal up the box so this fan pushes air though the box and out the PSU, with
it's fan removed and the vents enlarged, and also out the rear vent just
above the PSU which is just above the CPU. I could also add a louver over
the CPU area to get some air moving there. This would move more air across
the CPU, have a larger fan which should make less noise and still cool the
PSU.

The use for this box is doing multimedia (slide show/TV tuner) and most of
the time the HD isn't used nor is the system stressed at all, no 3D etc. I
guess I could try both and see, just wondering if anyone has some thoughts
on this.

If possible, use the PSU with 92mm fan, but mount fan on outside of power
supply... further from PSU components will reduce turbulence, and increase
airflow due to proximity to CPU. Flip fan so it's not blowing into case
but outward. Many power supply with fan on the underside still have vent
holes on their forward face. To get maximal flow out of the chassis you
can seal those vents partially or entirely, as well as sealing all other
chassis holes and gaps. If you do so and have a very porous filter
material, perhaps a piece of furnace filter, the chassis can stay
relatively dust free without reducing airflow as much as a finer filter.
Fine filters are great but all other things being equal they would reduce
airflow too much... it doesn't have to stay clean forever, a few years is
nice enough.


Don't bother trying to use only a pusher fan on the front, unless you
want to completely seal the case airtight, but if you wanted to seal it
anyway you'd still be as well or better off with only the rear exhaust
fan, it will pull more air though the heatsink but really ought to utilize
a duct. It is not necessary to use a massive heatsink but that that isn't
much smaller than a duct passageway, so a relatively large % goes though
the 'sink tines rather than around them.

Creating indirect path from noise source to outside the case, even
including use of insulation sheeting, will help reduce noise emissions, as
well as placing insulation behind the system when the power supply
exhausts.

Leaving a PCI slot case bracket cover off will allow more airflow past the
video card, but not more than one else you reduce airflow past the hard
drive and will be recirculating more and more of the exhaust air.

Hmmm, maybe a pic
http://69.36.189.159/usr_1034/generic_quiet.gif

Then again, most any cheap $5 Athlon heatsink with it's fan reduce to 5V
should be quiet while keeping a Celery 800 cool enough, and considering
the cost of a zalman plus the effort of fabbing a duct, might be a good
alternative.

kony wrote:


Hmmm, maybe a pic
http://69.36.189.159/usr_1034/generic_quiet.gif



That looks great... But the case I have (don't really want to buy another)
is the old style ATX case, where the PSU is mounted on it's side over the
CPU. I can't mount the 92mm fan outside the PSU, there isn't enough room.
I'm thinking the PSU with the larger heat sinks (more fins etc) will need
less airflow to stay at the same temp is the reason I want to use it.

Now I'm thinking maybe use the 80mm pull fan PSU and cut a hole in the
cover of it over the CPU and fabricate a duct of sorts to pull air across
the CPU HS. I'm -really- trying to avoid any sort of CPU fan, even the
stock intel fan at low voltage has an irritating whine, the larger fans
have more of a whoosh noise which isn't bad.

Thanx for all your advice!
--

Stacey

On Mon, 12 Apr 2004 22:03:49 -0400, Stacey wrote:

kony wrote:


Hmmm, maybe a pic
http://69.36.189.159/usr_1034/generic_quiet.gif



That looks great... But the case I have (don't really want to buy another)
is the old style ATX case, where the PSU is mounted on it's side over the
CPU. I can't mount the 92mm fan outside the PSU, there isn't enough room.
I'm thinking the PSU with the larger heat sinks (more fins etc) will need
less airflow to stay at the same temp is the reason I want to use it.

The side-mounting of the power supply should still allow using a duct if
you definitely want to go with a passive CPU 'sink though it could be a
bit harder to measure as precisely, acheive a duct shape maximizing flow
though the 'sink.

It may be true that the power supply with larger 'sinks needs less
airflow, but with such a modest, minimal system, it probably won't be an
issue, either power supply should remain cool enough so long as it's
moving enough airflow to keep the CPU cool enough. Having the fan on the
bottom (side in this case) side instead of on the rear wall, even if
internal to the power supply, often allows less fan noise to escape the
case. In the end it may not matter too much though, the particular fan
used in either, it's RPM, may be the more significant noise issue, you may
need to modify that fan rpm to suit your ears. The easiest way to do that
after the whole box is completed, up and running, might be a 100 Ohm, 5W
rheostat on the fan power lead, giving an incremental adjustment.



Now I'm thinking maybe use the 80mm pull fan PSU and cut a hole in the
cover of it over the CPU and fabricate a duct of sorts to pull air across
the CPU HS. I'm -really- trying to avoid any sort of CPU fan, even the
stock intel fan at low voltage has an irritating whine, the larger fans
have more of a whoosh noise which isn't bad.

Thanx for all your advice!

The intel fan is indeed quite whiney, it annoys me that they couldn't come
up with better than that, as Sanyo and Nidec do make better fans.

At some point intel switched from a smaller celeron heatsink to a larger,
i don't recall which came with the celeron 800... some were smaller, think
40-50mm but the later, larger were 60mm. If you can cut out the center of
their proprietary fan bracket or find an alternate method of mounting a
fan (for example tiny holes in the side, metal screws and L-brackets or
electrical straps) you could mount a fan like a Panaflo 60mm L1A, though
some don't come with an appropriate connector, would need a tail or to
splice on the leads from the original fan.
http://store.yahoo.com/directron/60l1a.html

With the "larger fans" you mention or even with the Panaflo, for lowest
noise you may still need to reduce voltage to the fan or use any
ready-made fan controller. The fan could run at a VERY low RPM and be
inaudible. It's sometimes possible for that solution to be even quieter
than a passive heatsink, because the power supply fan isn't needed to spin
fast enough to passively cool the CPU. Noise reduction is often about
reduction of the loudest part, then the next, in turn... The power supply
fan should (would typically) be the primary source of noise. You might
first focus on the power supply, getting the fan running at loudest
tolerable speed (keeping in mind that it may spin even faster in the
system rather than on a bench if it has thermal speed control for the
fan), then with power supply "finished" you can determine if that's
adequate for cooling the CPU passively, or if the CPU 'sink still needs a
quiet fan. If the CPU 'sink needs a fan the same factors apply as with
higher-heat cpus, to use the largest fan the heatsink will accept,
including thickness, and go from there reducing it's RPM. Since Celerons
do have an integral thermal shutdown mechanism it shouldn't be too bad if
it runs overly hot, the gradual overheating from an inadequate heatsink is
plenty slow enough for it's thermal diode to respond, unlike powering up a
CPU with no heatsink.

kony wrote:

kony wrote:


The side-mounting of the power supply should still allow using a duct if
you definitely want to go with a passive CPU 'sink though it could be a
bit harder to measure as precisely, acheive a duct shape maximizing flow
though the 'sink.



Well tonight I put it together, used the 80mm rear mounted supply with a
47ohm resistor on the fan, cut a hole in the side over the CPU (no duct)
and installed a 3100 zalman flower on the CPU (it's suposed to cool an
XP2000 with a slow 92mm fan blowing over it). After a 1.5 hour movie using
a software DVD player at 1280X1024 display size, the CPU temp was only 45C.
Maybe in hot weather it might be warmer but now the box is so quiet once
the hard drive spools down you can't even tell its running!!! I might play
with the other PSU and/or a duct if I start seeing temps over 50C. Thanx
again for your help, now I'm going to start working on my other machines!!

--

Stacey