[vdr] Re: cpu cooling

["Sven Karlsson" <svenka@it.kth.se>]

Hi again,

> > The PSU is a special low noise one from Q Technology. I think SilentPC
in
> > Netherlands have these. The fan in that one has been replaced by a Papst
> > 8412. The voltage on that fan very rarely goes above 7-8V!
>
> Regulated fans seem to be louder as the ear registers the changing of RPM
> much more than a slightly noisier fan running on constant RPM.

The Q Technology PSU doesn't have those sympoms. At least not when running
under light load as this one is running. It goes up to working temperature
and stays there. The working temperature corresponds to 7-8V depending of
the ambient temperature. I've run tests on the fan voltage and it stays
within 0.02V over an hour. I cannot notice the change in pitch.

The Papst fan is very silent and runs at 1500RPM at 12V which would suggest
625RPM at 5V and 1000RPM at 8V. Papst reports that the noise level is 12dB.
However, I do not know the reference point for this as it is clearly not an
absolute value.

Besides, as I said, my vcr is more noisy. Even my mobile phone recharger is
more noisy! You can't hear the fans at all. If you press your ear _directly_
to the box you can hear a slight humming noise which I suspect come from
mechanical vibrations from the PSU fan. The fan itself is silent. I haven't
experimented with rubber bussings although that might very well help.

However, being a perfectionist, I would like to put a completely fanless PSU
in it. Do anyone know of any good one? The only one I've seen are either of
rather low power (100-120W) or very difficult to work with.

I have experimented with removing the fan from larger (430W-600W) PSUs but
only had dissipointing results. The PSU ran _extremely_ hot and I couldn't
leave it on for long. Clearly, the heatsinks are too small, in the PSUs I've
tried, to handle passive cooling.

> One or to editions ago there was a list of silent and passive PSUs and
> silent fans int the c't.

C't is very hard to find in Sweden. Could you write down a few?

Best regards
 Sven