Power supply hot to touch - Page 2

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View

Re: Power supply hot to touch

Quoted text here. Click to load it

  The source for technical fact - that discuss CFMs and dB (another
significant parameter) - was cited.  You ignored them, then cited five
subjective sources.   See application notes from fan manufacturers.
Get parameters from any responsible fan retailer or datasheets.

  I applaud your efforts.  You tried to provide citations.  From those
citations, we all now appreciate why so many would have problems
comprehending my five point.  Subjective reasoning, for example,
insists that PSU fan direction is relevant to chassis cooling.
Direction is not.  Those educated by subjective reasoning get angry
when confronted by technical facts.   CFMs are not even mentioned in
your citations.  No numbers is how junk science gets promoted.  To
state that reality makes some people angry.  I don't care.  Even your
insult is not relevant.  You may choose to be frustrated and run
away.  Sorry.  But the only thing relevant here is science fact.
Either learn the facts or get angry and run away.  Your choice.  Learn
facts or act just like a George Bush supporter.

  Cited were useful sources - application notes from fan
manufacturers.  What says they will be useful sources?  They provide
equations AND they discuss actual numbers.   How many CFMs from a
typical 80 mm fan?  Those who learned this stuff would provide the
numbers.  25 or 30.   Provided here are numbers more useful than all
five citations.  Sources to learn that multiplication: text books,
manufacturer datasheets, or application notes from fan manufacturers.

   Direction of air through a power supply is not thermally relevant.
Even one of those subjective citations noted that.  Useful sources
provide actual numbers and equations.  A useful equation relates CFM,
incoming air temperature, watts, and chassis temperature.  Also
relevant is a dB parameter that is related to CFMs and fan size. Get
application notes and datasheets from fan manufacturers to grasp these
simple relationships. Then appreciate why those five citations were
uselessly subjective.

  Same fundamental apply to 'what is too hot'.  Once we had numbers,
then 130 degrees F was only warm - not too hot.  Another example of
distortion from subjective reasoning; not tempered by a perspective
called numbers.  It does make people angry when challenged because
they did not learn the numbers.  Angre occurs when subjective
reasoning gets exposed.

Re: Power supply hot to touch

On Mon, 3 Mar 2008 11:32:05 -0600, "Ken Maltby"


Quoted text here. Click to load it

What I meant was that there aren't any PSU made that blow
into the case instead of out, AFAIK, but even if there were
it would not make the PSU hotter it would tend to make it a
little cooler running at the expense of the rest of the
system getting hotter.

Instead what seemed more likely was that this is one of many
PSU that have the bottom fan but also have some slits on the
rear such that some of the intake air is  blown back into
case... this is usually not a big problem as it is a small
percentage compared to what is exhausted out the back, but
if the case intake is very poor or the PSU exhaust area is
mostly obstructed then the % would start climbing.  Overall
I still suspect a combination of poor psu and poor case
intake.



Quoted text here. Click to load it

Yes, taking  the case side panel off should improve the
situation but it should already be fairly obvious  whether
the case has ample front intake (and perhaps a side fan or
grate) or not.  I suppose we should determine for certain if
the PSU fan were really reversed and blowing the wrong
direction, but "think the fan is blowing into the case"
seems fairly ambiguous to me, it should be pretty obvious by
looking at the fan and the blade  slope/curvature, which way
it's blowing when spinning even if not powered so the fan
isn't spinning at the moment.


Quoted text here. Click to load it

That too, but given a fast enough fan the PSU still
shouldn't be that hot... just too noisey.  Then again "hot"
is a bit of a relative perception without a temp reading
number.  Even so, it takes a fairly poor setup for the PSU
casing to feel more than barely warm except when it's
completely off in S5 state the 5VSB current generation
without a fan running can tend to make some a little warmer.


Quoted text here. Click to load it

You'd certainly have less, but unless the rest of the case
were very poor and no passive intake (or exhaust in this
case) it should still be providing enough airflow that the
PSU doesn't get terribly hot, unless it's quite poor,
inefficient, or the fans aren't running fast enough.  

Note that most OEMs do use this "competing fan" arrangement
on the majority of their PC systems, with both the PSU fan
and the rear case/passive-CPU fan both blowing outward and
they manage to do it even without much noise.


Quoted text here. Click to load it

Absolutely, with one exception that the gain by doing this
can be offset by the increased noise emission having a fan
in the front where the sound can escape and be more easily
perceived by the user.  Even then, when that intake fan is
forced through the HDD rack it does a much better job of
keeping multiple drives cool.


Quoted text here. Click to load it

Hot air rising isn't much of a concern when it's being
actively moved by a couple fans.  More significant is what
you already wrote, that the intake (whether it be a fan or
just passive) and exhaust are at opposite *corners* of the
system as much as reasonably possible.



Re: Power supply hot to touch

wrote:


Quoted text here. Click to load it

While this may be true, some PSU just aren't worth the time
to fix or isolate failure point.  Slapping in a better new
PSU might be the answer if the case ventilation isn't
horrible.

Re: Power supply hot to touch

kony wrote:
Quoted text here. Click to load it

I was referring to an internal short inside a motherboard.
That could be drawing more current than normal from the
supply. Checking consumption, even if only with a Kill-a-Watt,
might give you some idea whether there is more to the problem
than a cheap power supply. I find a report of one blown supply,
and a second one running hot, to be suspicious. It might
not be the fault of the supply.

    Paul

Re: Power supply hot to touch

wrote:

Quoted text here. Click to load it

We don't know anything about the old one, but I would tend
to think a short in the motherboard would cause some
instability if bad enough to overtax a reasonably mated PSU.
Probably some melting of the connector block and
discoloration of the effected area, you can't burn off an
extra few dozen watts without some sign of it on the parts.

I wouldn't be surprised of a 3rd PSU blows if it is also
some generic 500W.  While the aforementioned system isn't
high end by today's standards it is hungry enough to wipe
out a junk PSU in anywhere from a few hours to a few
months... kinda the reason why they should be avoided.  I
suppose my main point is that until a known good quality PSU
is tried, and apparently the poor case ventilation problem
corrected, it would be hard to isolate the variables
further.  With the present PSU running so hot it certainly
won't have a good lifespan either way and ought to be
replaced even if there were some other component problem.

Re: Power supply hot to touch



On Sun, 2 Mar 2008 19:17:47 -0500, "Skeleton Man"

Quoted text here. Click to load it

Either:

A)  It's junk and will fail soon
B)  The fan and/or case intake isn't adequate for the load.


Quoted text here. Click to load it

??  If it has adequate exhaust area, that shouldn't be an
issue.


Quoted text here. Click to load it

This suggests the case itself impedes airflow, but it
doesn't necessarily mean the PSU is of acceptible quality or
capacity.


Quoted text here. Click to load it

I would not carry any confidence at all on only what bestbuy
carried.  There are ample PSU reviews online, if you can
take that PSU back for refund that seems the best option.


Quoted text here. Click to load it

The heat is a function of fan speed, when considering
external PSU case temp, but it is also likely it's cheap
junk and should be replaced.

Re: Power supply hot to touch




Quoted text here. Click to load it

  So you see no problem with a PSU that has fans blowing air
out, but no way for much air to go into the PSU?  Personally,
I would think competing fans might actually make the PSU
hotter.


Quoted text here. Click to load it

  True, at least in the since that the hot air from the PSU
had no place to go , but onto the CPU heat sink, with the
side on.  With the side off, there would be a path that allows
it to flow, and even hot air can carry away heat, if it is
moving air.

Quoted text here. Click to load it

   How about: it's a function of the air flow through the
PSU case?  If you have a box with competing fans;
where both are trying to blow air in or trying to blow
the air out, you aren't going to have much air flow.  The
best practice, with multiple fans, is to have intake fans in
one corner of the box and the exhaust fans in the opposite
corner, so the air flows through the whole box.  Since
hot air rises, it is natural to have the intake at or near the
bottom and the exhaust at or near the top.

  But you knew that, didn't you, Kony?

Luck;
    Ken




Re: Power supply hot to touch



Skeleton Man wrote:
Quoted text here. Click to load it

Some interpretations:

1) Your previous power supply blew. Perhaps the motherboard was overloading it.
    The motherboard could be overloading the current supply.

2) The supply is getting hot, because of a fault within the supply
    itself. There could be a short in there somewhere.

3) The power supply fan has stopped turning.

For (1), I would use the clamp-on DC ammeter I own, to measure
all rails, and see if excessive motherboard current draw is
present. Because the clamp-on meter is a non-contact device,
it can measure and characterize a computer rapidly, without
the need to snip wires.

For (3) you can check visually, as well as audibly. If the
fan slowed down, perhaps you remember it running faster at one
time.

For (2), that would be harder to check. I might disconnect the supply
from the motherboard, plug it into a Kill-a-Watt meter, and see
if the unloaded dissipation is in the 10W to 20W region or not,
with PS_ON# connected to COM.

In other words, if you really want to know what is going on,
it'll take a bit of test equipment. Slapping new power supplies
in there, over and over again, may not fix it.

A Kill-a-Watt meter is cheap, and is worthwhile to have around the
house. The clamp-on DC ammeter is much more expensive.

http://ecx.images-amazon.com/images/I/210M82BKVAL._AA183_.jpg
(Amazon.com product link shortened)

    Paul

Re: Power supply hot to touch



Skeleton Man wrote:
Quoted text here. Click to load it

I have no doubt that the PSU is cheaply built. Had you ever heard of
Dynex before you wandered into BestBuy?

But even a cheap PSU wouldn't be expected to blow hot air from its
bottom fan into the computer case -- it definitely should be sucking air
from above the CPU and ejecting it out the rear of the case.. Could be
that one of the assembly line workers was having an especially bad day
and inserted it backwards...

--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com

Re: Power supply hot to touch



Quoted text here. Click to load it

  First, the original ATX specs called for blowing air into the case
from power supply.  Later, that standard changed; reversed airflow.

 Second, relevant number is CFM through the chassis.  Basic science
(read application notes from fan manufacturers) makes it obvious.
Relevant to chassis internal temperatures is the parameter called CFM
and temperature where air enters the chassis.

  One standard 80 mm or 120 mm fan provides more than enough airflow
even assuming no heat gets transferred through a metal chassis.
Second fan (if in parallel) provides only a marginal temperature
improvement.   But it two fans are blowing in so as to reduce the
total CFMs, then a problem has been created.  Simplest answer for
chassis cooling starts with these numbers.  How many CFM are being
moved through that chassis?  Airflow direction is irrelevant. CFMs are
relevant.


  Meanwhile, as others noted, that power supply should not be hot to
touch.  Hot?  How hot?  How many have assumed 130 degrees F or
higher?   Without numbers, everyone must speculate.

Site Timeline