why not cheap a psu?

[KevinO]

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Robert.Wultsch@asu.edu wrote:
> Accepting that a cheap poer supply will only last 3 years (which I don't), I
> don't think that the average person will get 3-6 times the value out of an
> expensive psu.
>
They probably won't, but some will and I do.

<rant>
You may get 3-6 times as much damage out of a 'poorly built' one. (Actually
some vs none.) You may also get flakey or occasional problems that are very
hard to troubleshoot. I have been lucky and only had one cheap power supply
completely fail, but it only took about 8 months.

It depends, I guess, on what you are building and how your budget is. I have
bought cheap (and poorly built) cases and just used the supply that came with
it. I have also recently bought a couple Antec True 380s. They weigh TWICE as
much as the 'Fry's Special(tm) 300W. They were tested by Tom's Hardware

http://www6.tomshardware.com/howto/20021021/powersupplies-15.html

and shown to produce what their ratings say they can without catching on fire
or destroying themselves trying.(to catch on fire) They have variable speed
fans (two per supply) so they are quiet, move a lot of air, and can power up
to 3 case fans variable speed also. There is a small fan connector that can be
plugged into the motherboard and supply a fan rotation pulse thereby allowing
you to monitor the speed of a power supply fan using lm_sensors etc..

These went into our workstations. They are run 24x7 and each have multiple
HDs, lots of ram and fast (room-heating) processors. They have CDRWs and
DVDROMS. One has a zip and the other a tape drive. They both have power hungry
video cards.I expect these supplies to run for at least 20,000 hours before
needing attention. I suspect they will run for > 50,000 hours.

Most cheap, poorly built power supplies survive this long, in light duty.

Most power supplies can't meet the ratings that they have on their labels, but
it doesn't matter most of the time. The output needs to get pretty far off
spec. or noisy before you will know something's amiss -- unless you test for
it. Most machines have a single HD, a cdrom that gets occasional use and one
processor. A Toy(tm) power supply can meet the short and long term power needs
of this typical box. It won't have the cleaner output, the thermal control or
the load regulation of a better supply. (I have verified this using test
equipment.)

Listen carefully to a computer with a marginal supply and you can sometimes
hear the fan(s) speed up and slow down slightly. (They will usually speed up
slightly as the CPU load goes up.) Cheap supplies have little if any dedicated
regulation for the 12V rail. Your CPU starts drawing current at 5v or 3.3v and
the switching supply cranks up its' pulse-width to try to hold the high
current, CPU rail close to spec.. This makes the 12V rail rise a little bit.
The feedback loop that provides the regulation isn't watching the 12V rail,
and without a dedicated regulator for the rail it couldn't do anything about
it anyway.

But this is good enough most of the time.

My crappy Winder's box at work does this (Dell Optiplex GS-1). At least Dell
rated the toy for what it is (150W IIRC).

I have friends boxes that do this. The labels on their supplies say '300W'.

Different people will have different opinions of what a 'moderate' amount to
spend on a supply is. To me, spending $50 to get a 300W version of the 380s we
have is cost effective and moderate. I would spend a little more to run a pair
of Athlon's or PIIIs, multiple drives and a bunch of case fans....

I would spend $58 to get an Antec case with a 'mid-range' (still Antec, just
not as fancy) 300W supply to build a basic, single CPU machine. (Normal
workstation, small server or cluster node) I don't have access to any
significantly less expensive supplies that would work the same. I don't have
the time to look too hard for them either.

I don't see why people will sometimes pay more than $200 for a 'gaming' power
supply tho. A True 380 will run a pair of Athlon's -- no sweat. I hate to see
people spend $30 - $50 or more for a piece of crap supply from Fly's when it
is really a $15 or $20 value.
</rant>

The more boxes I build and maintain, the more I am willing to spend a little
extra to get better quality. Ten power supplies running will produce failures
more often than one or two running will.
- --
KevinO

A "few" is an indefinitely small number that conveys a qualitative sense of a
quantity, but not quantitative fact.
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