On Friday, October 22, 2010 03:12:03 pm Igor Chudov did opine:
> OK, thanks for saving my A$$ and giving me your first hand user
> experience. I will look for something else.
>
> Which is kind of sad really. How hard is it to put together a fanless
> system that consumes at most 20 watts and has a reliable power supply?
>
> i
>
The main problem, Igor, is the quality of the capacitors used. And without
actually specifying to the maker that your device is to be made only with
very low ESR, 105C rated capacitors, and paying that custom built premium
price, then one generally has to take his chances with new hardware.
Switching power supplies, (whether in a tin can called a PSU, or wrapped
around the CPU socket on the motherboard) which often have several hundred
watts worth of power being shuffled around through these capacitors, with the
load absorbing only 15% of that at any one time, and of course the actual
power input is, after getting everything running at powerup, is only that
15% scaled to the efficiency of the circuit at that load level. At low load
levels that efficiency is often far less than the 85% or more claimed for a
full load situation, sometimes as low as 10%.
The bottom line is that these caps must have a _vanishingly_ _small_ ESR
(Equivalent Series Resistance) because it is this characteristic that
determines 90% of the power losses (the other 10% usually being the ohmic
and iron losses in the inductors) of the heat generated within the
individual capacitor. The greater the heat generated from this resistance,
the shorter the life of that capacitor will be.
Those capacitors can be had, but at a 2 to 5x premium price that most mobo
and psu makers can't afford if their product is to be competitive.
We buy those better caps in bulk at the tv station, and routinely replace
the elcheapo crap used in quite a bit of the stuff sold through the channels
to broadcasters, often within 6 months of placing something into service.
Usually its a one time and forget it deal.
[...]
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Old Japanese proverb:
There are two kinds of fools -- those who never climb Mt. Fuji,
and those who climb it twice.
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