Having the habit to silence my PCs, I tried to make pegasos II even more quiet by removing the processor fan and adding an airduct. The task was much more easier than silencing an athlon or a pentium PC because I didnt have to use exotic hetsinks. Also the box and motherboard topology helped me alot. Everything is reversible so if a problem occurs I can change to the old cooling method. So here is what I have done.

I opened the Power Supply ... and


I lowered the PSU fan speed by adding in series an 82 ohm resistor.


I removed the "vga" heatsing and fan and installed a much bigger custom heatsink which was made from an athlon heatsin cut in half and installed an "airduct" so the power supply sucks air through the processor heatsink





The system is working fine for months now. It is very stable and ultra-quiet. It doesn't run hot even if compiling all day on hot summer days - thanx to low power processor.

have a look at this:

http://metadistribution.org/cooling



Pieter

The review at http://genesi.pegasosppc.com/files/press/ODW-Review.pdf says somewhere, that 'simply disconnecting the PSU fan puts and end to the problem'. Can I do that safely? Anyone using ODW this way?

CzP

I wouldn't recommend it as it removes the SOLE outtake fan in the system which means it will turn into an oven. The line mentioning the noise and the "solution" really shouldn't have been in the review in my personal opinion.

The ODW isn't as noisy anymore (the G4 fan is louder than the PSU once more) because we are shipping better PSUs in the systems but anyone who doesn't like the churning of the PSU fan can do the mod mentioned here for a SAFER solution. It is MUCH preferred to have air blowing out of the case, and if the PSU gets too hot (it will get hot..) then it's components will last less time and may get unreliable.

You'll void your warranty though, doing any mod to these power supplies, we would charge you for the replacement PSU if you destroyed it. They're about $30 to replace.

--
Matt Sealey
Genesi, Manager, Developer Relations

Hello,
I found this idea also very strange, but as I found it on the 'official' Pegasos website, so I couldn't resist to ask...

I have an 'old' ODW, so here the PSU makes most of the noise. (and the DVD, when it starts....).

CzP

Just like Neko said; airflow is crucial. Today the
processor is not the real problem - If you have an
x86 you know you must have proper cooling. What
many people forget are the harddrives. Drives today
are running at up to 50 'C when working. Imagine
that temp all day long, 24 hours a day. People
insert minimal cooling in their desktops and complain
about harddrives failing?..

In small MicroATX boxes there is seldom any other
casefan than the PSU fan. Don't fiddle around with
it! In bigger cases this isn't as much of a problem
since they usually have space for fans.

The easiest approach for quieting down the G4 CPU
is exchanging the fan to a 40 mm Papst (12 dB) or
ADDA (14 dB). If you hear 12-14 dB.. Well..
Join the Army.

Indeed.

The best heatsink in the world is AIR

I will let you all in to a little dirty secret of ours which is that we changed the ODW case without testing it first. The white pearl chassis we now use was picked because of it's clicky drive door (that doesn't fall off in transit), smaller dimensions, not-so-expandable drive bays (you can't install a second optical or hard disk.. floppy bay stuff only. But we plan to fill it with a standard and internal smart card reader at some point anyway) it kind of seemed like a compromise for a less "cool" case but one that was worth making. We also thought we'd be able to get it in black.

What we found when we were building them to order is that the power supply was LOUD. We made an experiment to cut the PSU fan and see if it would make much difference; and it practically didn't. The PSU gets boiling hot but the system is really stable even in bad air conditioning. This is where Jason (Linux User & Developer Magazine) got the idea from, so you can blame me - a compromise I thought would be to connect the chassis fan and use that to draw air out, and this cooled the system down considerably with VERY little noise.

Fortunately our case supplier changed the PSU on us about 4 weeks ago. It now has a SATA connector which is making us giggle with joy, and a fan which is quieter than the CPU fan on the G4 card (and by that I mean both the version with integrated fan, and the one with the top-mounted fan).

Therefore there are now 3 kinds of ODW in the world - ones with AOpen blue/grey cases, ones with the beige case with a loud PSU and ones with a beige case with a quiet PSU. AOpen users are fine. The second set of beige ODW users are fine.

If users have the loud PSU version and are DESPERATE for lower noise, what I UNOFFICIALLY suggest is to follow the suggestions above and add a 70 or 80 ohm resistor (forgive me I don't recall the correct series numbers right now, my physics classes were all of 8 years ago). Also connect the chassis fan (if you have a modern Pegasos II it will connect it's fan to the motherboard, so buy an adapter) because if you don't, your PSU will flood the case with hot, still air, and your drives will start to bake. You HAVE to connect the chassis fan. It's to do with air pressure, and the way these cases are designed to draw in "new air".

It's that simple

Anyway this is all UNOFFICIAL and you will void your warranty on the case and PSU if you mess around with it, and if your CPU card burns we may giggle at you for a while before sending you a replacement. Be warned, be wary, but have fun

--
Matt Sealey
Genesi, Manager, Developer Relations

NEVER EVER remove PSU fan! I am an electronics engineer and have seen many horrible compiter deaths happened due to cooling fault.
First, temperature in the case goes high and capacitors start to bake. They lose their capacity and your motherboard becomes unstable. In the worst case PSU's capacitors (this is THE CASE when you remove PSU fan) do this too. This can lead to any consequences depending on your PSU model. Again, in the worst case, parameters of the voltage generator go completely out-of-specs and it can produce for example +6V instead of +5V. Guess what happens them...
The second scenario. PSU is strong, it works, but gets hot like an oven. In one sad moment... BAH!!! Some electrolythic capasitors explode. During this process they usually short-cirquit. Then, again, everything depends on what is shorted and where. You can either lose 2 transistors or your +5V traces from the PSU to the exploded case can burn out. Depenging on quantity of burned traces the board can become irreparable.
So, for the first, i would suggest to modders first to create some temperature monitoring system. There is SM-Bus in the Pegasos, it mostly sits unused since only SPD chips are connected to it, there are no built-in temperature sensors (i checked this using lmsensors package), but there is a possibility to hook up an external SM-Bus compatible sensor to the bus and make use of it (with the same lmsensors software).

hi , i realise the last post was a long time ago now but i wonder sometimes what is the better option to
quieten your average PSU, hopefully you might clarify it for the readers and me ?.

the assumption is that the modder is aware that its VERY Dangerous messing with the HV stuff inside the PSU so dont do it!, the average fan is 12v dc so providing your careful you might mode it to a better spec.

what i wonder is, is it better to put 2 standard 12vdc fans in the PSU case in series so as to lower the rotation
of both (placing them at eather end of the case) but
keeping the average aireflow.

or putting 2 12vdc fans in parallel and reducing the
voltage to each seperatly with a resister(variable ?)

would it be easyer to just feed them from the 5vdc line and would that be the better salution for getting that elusive super low db without fear of the PSU doing POP ?.

also would the same idea work for the CPU i,e placing 2 slower fans at both sides of heatsink
drawing air across it in the same direction ?.

I did a simple modification on my own, and it works. What you don't see on the pictures is that I remove the mini-atx power supply, and replaced it with a silent ATX power supply. It doesn't fit in the box, but I let it be outside, it has long enough cables. Result : 0 fans, silent (only the hardrives makes some very low noise, seagate ones).





cheers,
dams

Too bad your data will be gone in a year or so.
Not many people listen to what I have said the last years.

"CPU cooling is not an issue anymore since everyone
knows it must be cooled, one way or another. Harddrives
is the problem of today. Without any airflow in the case
they will be hot as hell and die prematurely."

The air will easily be 50-60'C inside a small ODW-case
with no airflow. The harddrives are around 40-45'C when
running + the fanless CPU at maybe 60-70'C. If you ever
touched the heatsink of a G3 you know they are hot.

I'm monitoring my harddrives. Their temperature is around 50 C, which is under the 60 limit of this harddrive model. And smart will warn me before any critical problem, hopefully.

What is the temperature of your CPU (or heatsink near the CPU Die) after running dnetc for an hour?