[gentoo-user] Re: new machine : case + power

[james]

Nikos Chantziaras <realnc <at> gmail.com> writes:


> However, note that PSUs tend to go bad after years of operation. An 8
> years old PSU might start losing power or voltage stability. If you see
> random machine resets or hangups, it's usually because the PSU is dying.

Very true. However, if you are "handy with electrical wiring", DC voltage
analysis, live, is quite simple. Just monitor the voltage outputs, under 
load with a "multi meter" and see if the voltages sags below the unload
rail (dc voltage level). Also the most common failure of PC style PS
is the fan and those can be changed for a few bucks. But electronics do age
and a good UPS will extend the life of your PS. UPS batteries, typical
a 7-10 Amp-hour are cheap to replace ever 2-4 years. Another simple way
to do this, and more cool, is the get an amp meter. Just convert the
wattage rating of the PS to an amp rating at a given voltage level. Clamp
around the power cord running to the PC and you can see the static (non
transient) voltage sag if it occurs as the amperage draw increases.
If you can find an old analog meter, with a needle on the dial, you can
see a transient energy draw by the fast movement of the needle on the dial.
Digital meters that can do this, or capture the traces (as in an
oscilloscope) are much more expensive, but makes for a fun lab to learn
about the operational characteristics of dynamic electrical energy flows.
(trying to keep this non-pedantic).




> With that GPU, you don't need more than 400W. And the amps on the 12V
> rail are also not important, as that only comes into play with
> higher-end GPUs. Other features can still be important though, like
> protection against surges and such (think lightning strikes that can
> potentially damage your PC, or some PSU malfunction that could do the same.)


True, but you are not considering transient voltage swings. If your rig
draws 350 W and you have a 400 W PS, you will get spikes and draw-downs
on the voltage during transient period of peak usage. This will kill a PS
over time, faster that if the 350W rig is running off a 500W supply.
Lots of quality capacitors in the PS minimize these effects. If the PS
is rated as extremely efficient (compared to other PS) then it has
better quality components inside the PS (they react faster to transients).

caveat emptor! Size does matter for a long and happy life::
;-)	


James