Power supply fan airflow direction

On Sat, 28 Jun 2003 18:55:39 GMT, kony wrote:

There are people who claim it shouldn't be done, that there's a change
the 5V will be shorted to 12V and fry components. I and many many
others have been doing this for years and never had a problem...

You can put at fuse or a small resistor i series with the fan
and you can forget that type of problem.

On Sun, 29 Jun 2003 00:11:31 +0200, Ken wrote:

On Sat, 28 Jun 2003 18:55:39 GMT, kony wrote:

There are people who claim it shouldn't be done, that there's a change
the 5V will be shorted to 12V and fry components. I and many many
others have been doing this for years and never had a problem...

You can put at fuse or a small resistor i series with the fan
and you can forget that type of problem.


A diode will also work if ~56.5V is acceptable (almost, if not all 12V
fans will still spin-up at 6.5V), but often I quickly assume many
people aren't willing to get out the soldering iron or don't have the
minimal level of electronics experince or have the parts available...
in that situation a new quiet fan might be worth the $.



Dave

On Sat, 28 Jun 2003 22:42:33 GMT, kony wrote:


A diode will also work if ~56.5V is acceptable (almost, if not all 12V
fans will still spin-up at 6.5V), but often I quickly assume many
people aren't willing to get out the soldering iron or don't have the
minimal level of electronics experince or have the parts available...
in that situation a new quiet fan might be worth the $.

Hmm, nevermind, I'm wrong, and a major typo too.


Dave

kony wrote:

It was not a stamped in grill. I don't know what to call it, but I think
if it's not a stamped in one, there's only one left.

Chrome wire grill?

Hmm, perhaps it's a stamped in after all. It has the shape and looks of a
chome wire, but it's infact stamped out of the casing. I just asumed that a
stamped grill was a plate with round holes in it.

I didn't cut out a hole for the extra fan, and I don't know if I will.
There is not enough room for a 80x80mm fan, because of a transformer
that's mounted on the bottom-plate.

You're talking about mounting the fan inside the casing, right? I was
suggesting the fan mount to the outside of the casing, which is also
quieter. If a portion of the casing-side facing the motherboard is
obstructed by a PCB mounted upside-down, parallel to the "bottom" PCB,
you might still benefit from the fan, though it could have a bit more
noise from increased turbulence.

No, I was talking about mounting a fan on the outside of the PSU. But I
can't cut a hole in the casing, because then the transformer will fall out.

There are people who claim it shouldn't be done, that there's a change
the 5V will be shorted to 12V and fry components. I and many many
others have been doing this for years and never had a problem... I
think the odds are higher that you'll be in a car accident or struck
by lightning, but if it worries you then use a few diodes or a power
resistor in-series on the positive fan lead, it'll drop the voltage
too but experimentation will be needed to determine the optimal
voltage drop, components needed per each type/brand/size/airflow/etc
of fan to achieve the desired result. Some higher-powered fans will
also run at 5V, so you could use the adapter I suggested above without
these issues, but it's hit-or-miss if the fan produces the few-low RPM
you want but still has enough torque to spin-up at power-on. It's a
whole lot easier to use these alternate methods if you have a box of
different fans sitting in front of you and some pre-made adapters with
different values of resistors, or a voltage adjustment pot to
"dial-in" the value you need for the power resistor.

I think I'll stick with a resistor then, I don't like taking risks. When you
know the amps usage at 12v, you can guesstimate the needed resistor value,
and I have loads of resistors here, so that's not going to be a problem.

Well, I think I've learned enough to stop bothering you with questions .
I'll experiment with fans an perhaps some additional heatsinks on voltage
regulators and perhaps on caps.

Thanks for you time.

Halfgaar
--
To send email, change nospam.com into yahoo.com.

On Sat, 28 Jun 2003 22:42:33 GMT, kony wrote:

There are people who claim it shouldn't be done, that there's a change
the 5V will be shorted to 12V and fry components. I and many many
others have been doing this for years and never had a problem...

You can put at fuse or a small resistor i series with the fan
and you can forget that type of problem.

A diode will also work if ~56.5V is acceptable (almost, if not all 12V
fans will still spin-up at 6.5V), but often I quickly assume many
people aren't willing to get out the soldering iron or don't have the
minimal level of electronics experince or have the parts available...
in that situation a new quiet fan might be worth the $.

No, a diode will not act like a fuse that the resistor will do
if you are connecting the fan between +12V and +5V.

Ken wrote:

On Sat, 28 Jun 2003 18:55:39 GMT, kony wrote:

I would trust the case manufacturer's design TOO much.. after all, in
a traditional mid-tower case with PSU above the mobo, there's still
good reason to have a fan behind the CPU on the rear case wall, and
both Intel & AMD as well as most of the OEMs promote this design too.
I can't really speculate about how low the temps will be, it's a
unique system in a sub0optimal case and there's the ambient temps to
consider too. You'll just have to try a few things and see the
results.

My case is an example, I made a modification to put in another fan
in the rear och now it's 3 fans (inluding PSU fan) and two fans
in the bottom front to cool the HDD:s
http://w1.857.telia.com/~u85710476/docs/pcny51se.html
(My PC building project is not completed yet)

Isn't this going to make a hole lot of racket? Or are all the fans running
very slowly? It's going to be cold though...

BTW Kony, I talked about my PSU being next to the mainboard. In Ken's
pictures, it's where the two blue rear fans are. As a result, my case is a
little bit lower. A case like yours, ken, would be much better than what I
have. And it looks cool too. Is it a Lian-Li?

Halfgaar
--
To send email, change nospam.com into yahoo.com.

On Sun, 29 Jun 2003 22:29:59 +0200, Halfgaar
wrote:

My case is an example, I made a modification to put in another fan
in the rear och now it's 3 fans (inluding PSU fan) and two fans
in the bottom front to cool the HDD:s
http://w1.857.telia.com/~u85710476/docs/pcny51se.html
(My PC building project is not completed yet)

Isn't this going to make a hole lot of racket? Or are all the
fans running very slowly? It's going to be cold though...

The backplate fans is normally going to run relatively slow
and they are temperature regulated from the Antec PSU. Very quiet.
The two front fans have a manual 3-speed switch (Lian-Li standard)
but I planning to build a separate manual adjustable and temperature
controlled ciruit for the front fans. (I'm an electronic engineer)
Silence is very important for me.


BTW Kony, I talked about my PSU being next to the mainboard.
In Ken's pictures, it's where the two blue rear fans are.
As a result, my case is a little bit lower. A case like yours,
ken, would be much better than what I have.
And it looks cool too. Is it a Lian-Li?

Yes it's an Lian-Li PC68. (click on image and you get the answer).
I choose the PC68 model for it's good ventilation intake in the front.