why not cheap a psu?

[Michael Havens]

You know what; I have heard my fan slowing down and speeding up=2E
:-)Mike(-:
----- Original Message -----
From: KevinO
Sent: 4/10/2003 4:39:53 AM
To: plug-discuss@lists=2Eplug=2Ephoenix=2Eaz=2Eus
Subject: Re: why not cheap a psu?

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Robert=2EWultsch@asu=2Eedu 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=2E
>
They probably won't, but some will and I do=2E

<rant>
You may get 3-6 times as much damage out of a 'poorly built' one=2E (Actually=

some vs none=2E) You may also get flakey or occasional problems that are very=

hard to troubleshoot=2E I have been lucky and only had one cheap power supply=

completely fail, but it only took about 8 months=2E

It depends, I guess, on what you are building and how your budget is=2E I ha=
ve
bought cheap (and poorly built) cases and just used the supply that came with=

it=2E I have also recently bought a couple Antec True 380s=2E They weigh TWI=
CE as
much as the 'Fry's Special(tm) 300W=2E They were tested by Tom's Hardware

http://www6=2Etomshardware=2Ecom/howto/20021021/powersupplies-15=2Ehtml

and shown to produce what their ratings say they can without catching on fire=

or destroying themselves trying=2E(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=2E There is a small fan connector that ca=
n 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=2E=2E

These went into our workstations=2E They are run 24x7 and each have multiple=

HDs, lots of ram and fast (room-heating) processors=2E They have CDRWs and
DVDROMS=2E One has a zip and the other a tape drive=2E They both have power =
hungry
video cards=2EI expect these supplies to run for at least 20,000 hours before=

needing attention=2E I suspect they will run for > 50,000 hours=2E=0D=0A
Most cheap, poorly built power supplies survive this long, in light duty=2E

Most power supplies can't meet the ratings that they have on their labels, b=
ut
it doesn't matter most of the time=2E The output needs to get pretty far off=

spec=2E or noisy before you will know something's amiss -- unless you test f=
or
it=2E Most machines have a single HD, a cdrom that gets occasional use and o=
ne
processor=2E A Toy(tm) power supply can meet the short and long term power n=
eeds
of this typical box=2E It won't have the cleaner output, the thermal control=
 or
the load regulation of a better supply=2E (I have verified this using test
equipment=2E)

Listen carefully to a computer with a marginal supply and you can sometimes
hear the fan(s) speed up and slow down slightly=2E (They will usually speed =
up
slightly as the CPU load goes up=2E) Cheap supplies have little if any dedic=
ated
regulation for the 12V rail=2E Your CPU starts drawing current at 5v or 3=2E=
3v and
the switching supply cranks up its' pulse-width to try to hold the high
current, CPU rail close to spec=2E=2E This makes the 12V rail rise a little =
bit=2E
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=2E

But this is good enough most of the time=2E

My crappy Winder's box at work does this (Dell Optiplex GS-1)=2E At least De=
ll
rated the toy for what it is (150W IIRC)=2E

I have friends boxes that do this=2E The labels on their supplies say '300W'=2E=


Different people will have different opinions of what a 'moderate' amount to=

spend on a supply is=2E To me, spending $50 to get a 300W version of the 380=
s we
have is cost effective and moderate=2E I would spend a little more to run a =
pair
of Athlon's or PIIIs, multiple drives and a bunch of case fans=2E=2E=2E=2E

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=2E (Normal
workstation, small server or cluster node) I don't have access to any
significantly less expensive supplies that would work the same=2E I don't ha=
ve
the time to look too hard for them either=2E

I don't see why people will sometimes pay more than $200 for a 'gaming' power=

supply tho=2E A True 380 will run a pair of Athlon's -- no sweat=2E I hate t=
o 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=2E
</rant>

The more boxes I build and maintain, the more I am willing to spend a little=

extra to get better quality=2E Ten power supplies running will produce failu=
res
more often than one or two running will=2E
- --
KevinO

A "few" is an indefinitely small number that conveys a qualitative sense of a=

quantity, but not quantitative fact=2E
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