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Old July 9th 18, 07:43 PM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
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Posts: 1,467
Default Can I make my power supply fan turn faster?

lid wrote:
The fan is making noise. I can stop it with a pencil. I sprayed a
jet of wd 40. It is a little more quiet. I think if I could get it
spinning faster and give it one more burst, it might hit the spot.


That's exactly the wrong lubricant.

WD40 is a penetrating solvent, for loosening rusty this and that.

Even 3-in-1 oil, isn't an ordinary lubricating oil.
While it may indicate electric motors on the can,
it might not be the absolute best lubricant for the job.

The oil in your car, is getting closer to a real lubricating
oil. You need to select a viscosity for the job (too
thin, just pours out, too thick, it causes some
friction on the motor hub). for example, my old
tin of bicycle grease, the brown stuff, might
stick around... but it also might "stick around".
It would be hard to apply without a pressure fitting
and a pump.

In any case, you'll notice from overclocker threads,
that brushless DC cooling fans are voltage sensitive.
They spin slower at 7V than at 12V.

PWM (four wire, really small connector), those have
a speed control determined by the fourth wire. The
signals include

GND
+12V
RPM_signal (output) - two pulses per rotation
PWM signal (input) - square wave, duty cycle indicates desired speed

The CPU fan header on modern motherboards tends to have a PWM signal.

When the PWM signal is unconnected (plug four pin fan into
three pin motherboard), the fan spins full speed.

When you plug in a three pin fan to a four pin motherboard
header, everything is normal as far as the capabilities
of the fan go.

On older three wire fans, the signals are

GND
+12V
RPM_signal

and there is no speed control. Adjusting the 12V any where
between 7V and 12V provides a measure of speed control.
Maybe a ten year old motherboard, has a three pin connector
for the CPU fan, where the +12V power is adjustable.

Ventilation fans, such as remove air from the computer
case, have these fewer signals. There is no RPM signal available
to monitor whether the fan is spinning or not. These are
*very* common. Odds are, this is your fan. Note that,
this fan isn't practical to use on the CPU fan header,
because the motherboard will "whine" about no fan
being present, unless it sees RPM_signal pulses
coming out of the CPU fan. Generally the CPU fan is
the only fan header which is full-featured. Adjusting
the voltage on this, will control the speed.

GND
+12V

The ATX power supply doesn't have ready-made voltages
for lab experiments.

For the amount of dicking around it would take to
make you an "electronics lab" for this little
project, you might be able to pick up a replacement
cooling fan at the computer store. I realize in 2018,
there aren't a lot of good candidates. I was shocked
at the crap for sale at my one good computer store,
when I went looking for spares. I ended up with some
fans with ugly blue LEDs, which is not really what I
wanted.

The absolute best fan at the time a few years ago,
was Vantec Stealth. They've lasted nicely for *years*
here, but I don't think Vantec sells them any more.
Of the four speeds, low, medium, high, ultra, the
Stealth is a low. Your fan is probably a medium,
so that wouldn't be an exact substitute anyway.

High and ultra are too loud. I own one ultra, an impulse
buy, and it has a nice metal body. It runs around
110CFM and sounds like a mini vacuum cleaner.

The medium will be around 35CFM.

A low would be somewhat less than that.

The medium and low will be less than 30dBa. Fans
over that dBa level, have the potential to annoy.
To use the ultra, I used to run it at 7V. It's
currently out of the computer case, and some other
fan took its place.

The ultra was thicker. 37.5mm thick. Convention fans
are 25mm thick (one inch). Your fan will be conventional.
They do make 15mm fans, which are sometimes used on
low profile blow-down CPU coolers. The thinner the fan,
the less CFM cooling.

Fans also come in standard square dimensions. Such
as 80mm and 120mm. You need to measure the fan with
your inch ruler, and multiply by 25.4mm per inch.
Also, verify the four mounting holes for the
screws are in the standard locations. Some fans
do weird things with the corners, and you have
to keep your eyes peeled for stupid stuff. Fans
almost have defacto standards... except when they don't.

Sometimes you can guess at the energetics of the fan,
based on the current flow number printed on the fan
hub label. Like, if you took the fan to the computer
store, the clerk might look at the hub label, and the
overall design, to select a substitute for you.
My ultra is 1000mA. The Stealth might be 100mA.

There are a lot of fiddly little details, but nothing
you can't handle if you're observant.

Also, look at your motherboard manual, to see what
fan header capabilities you've got. Maybe simply turning
down the fan, via some BIOS setting will be enough.
Some BIOS had quite fancy thermistor versus RPM
rate controls, and they adjust the fans according
to thermal conditions. The SuperIO chip actually has
an automated "thing" to do that.

Or in Windows, use Almico Speedfan (which will re-program
the registers on the SuperIO). If you have PWM
or motherboard voltage control fan headers, you could
turn the fan down a notch and see if the noise stops.

http://www.almico.com/speedfan452.exe

( http://www.almico.com/sfdownload.php )

Speedfan can only control fan speed, if the motherboard
fan headers have the right electronics to support speed
changing. Don't expect miracles. From a percentages
and betting perspective, most chassis cooling fans
won't respond to a Speedfan setting. If you have
a primo setup, you might get lucky :-)

Most of the time, the confluence of factors means
that fan you didn't describe in detail, doesn't
actually have speed control. And you have to be
handy with a soldering iron, if you want to prove
them wrong.

You can get a rheobus for a 5.25" tray in the
computer, and it comes with knobs you turn to
adjust fan speed. But these have gone out of
favor, and there might not be much on a site
like Newegg to choose from. Only a couple
designs were exemplary, having a 2 amp per
channel control capability, and those could
handle anything. The rest were "schlock" and
had wire-wound pots or something, a really cheap
and not so good method. The cheesy ones could
burn out easier.

This is a sample of a rheobus. OK, great, it
has eight channels. It's 8 channels for $85.
If they'd made a 4 channel one, it would be
$42 bucks. And if they made a 2 channel one
(enough for the cheapest computerist), they
could have made this for $21 bucks. I bet
they've sold zero of these... "Maybe Bill Gates
owns one." Still, their heart is in the
right place, as it has a 30W per channel rating
(a bit more than 2 amps at 12V).

https://www.newegg.com/Product/Produ...9SIA17P5RA7928

Paul