Failure to POST: mobo or power supply?

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Months ago one of my main computers running winXP crashed.  At first I
thought it was a software issue, and reinstalled XP.  However, the
video seemed to struggle upon installation.  So I put in a another hard
drive and installed Ubuntu Linux.  It worked fine for a few days and
then the video on the monitor also begain to freeze and lock up the

Now, I can't get the computer to POST and the mobo complains about the
AGP slot.

The problem is that no matter what video card I put in, the video card
fan will not spin.  So that rules out the problem being the video card.
 So my question is, how do I determine if the problem is the
motherboard or the power supply?

Everything else works fine, so that leads me to think the mobo may be
the problem.  But how can I be sure of this?

My mobo is an Asus A7N8X Deluxe

This computer isn't old old, and I have already bought a new machine
for my main needs.  But I would like to bring this machine back to life
as it would be good as another extra computer.  I don't want to spend a
lot of time tinkering around trying to fix it if I could spend ~$100 to
replace the correct part(s).

Thanks for any advice,

Re: Failure to POST: mobo or power supply? wrote:
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Check for bad caps on the motherboard. These are the usually blue or
black plastic covered post like things that stick up vertically from the
motherboard. The tops should be flat, if any of them have bulged or
have leaked, those are the bad caps and are the cause of the problem.

It isnt generally practical to do anything more than
replace the motherboard if that is the problem.

Re: Failure to POST: mobo or power supply? wrote:
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It's etiher Bad Caps, or bad agp gontroller/agp slot.
Both of these are a motherboard-level problem. AGP controller issues
can be worked around by the simple expediant of using a PCI card.  Bad
caps=new motherboard, and bad agp is SHOULD get new motherboard.....

Bad caps is MOST likely. A compatable motherboard can be had, check
local computer shops if they have any New Old Stock around.  It's
something you have to ask for.

Re: Failure to POST: mobo or power supply?

On 19 Sep 2006 06:31:17 -0700, wrote:

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What _exactly_ does "seemed to struggle" mean?
These are key details and you're leaving them out.

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Video freezing means what?  Whatever is on screen remained
static?  Was there any system activity resulting from mouse
or keyboard input?  I don't mean video changing, I mean like
trying to shut down with <Win><U><Enter> or other commands?

Video freezing could be one of many things, like a power
supply problem crashing the system, or motherboard, though
seldom the video card itself (though possible?).

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If it won't POST, how can it be complaining about the AGP

You need to tell us exactly what you are observing instead
of the summary conclusion.

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... and at this point, what else is or isn't happening?

My point might be that video doesn't usually freeze because
of the video card, as the video card is still actively
sending that signal to the monitor- if it were not, the
monitor would be blank.  Even so, video cards can fail in
different ways, it would be good to try another one.

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No, it does not rule out a video card problem, but it does
suggest there might be something else wrong.  In other
words, the video card is probably fine but only having it
working, in a runnning system, rules it out.

One possibility at investigating this situation would be to
unplug the video fan, use a multimeter to check the fan
header output (voltage), and trace back that subcircuit to
the AGP connector pins (probably 12V), and with the board
out of the case, measure that connector voltage on the back
of the board.  It is not exactly easy to prop up a board,
have it running, and probe these connections though unless
you have a jig set up to suspend a board with the back
exposed, but I mention it because sometimes directly
following a fault backwards you can find where the problem
starts, and it can take creativity in deciding the best way
to do it, ways seldom mentioned as generic PC
troubleshooting tips.

If using a multimeter is beyond your skill level, then what
remains beyond stripping the system down (as mentioned
elsewhere in the thread) is swapping parts- either those
available or by purchasing other parts (preferribly from a
place with a good return/refund policy).

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In that non-POSTing, non-running state, use a multimeter to
check PSU voltages.

Unplug the system from AC power for at least 10 minutes, and
pull the battery at the beginning of AC disconnected, or use
the clear CMOS jumper.

If nothing else helps, begin stripping system down to bare
essentials- leaving only CPU, heatsink/fan, 1 memory module,
and video.

At this point it should be noted that you failed to do
something very important- start out your post with a concise
but complete description of all major parts, including the
PSU make, model, wattage, and the exact CPU you used (as
some A7N8X may have a rare problem with mobile bartons- I
still have one of these boards somewhere that only posts
about 1 time out of 12 with a mobile barton, but runs fine
with same barton far overclocked IF it posts, or always
posts with another pre-Thornton Athlon XP.

If you have another video card, particularly an old PCI card
(being more compatible with legacy modes due to PCI, and
also more likely to use less power), disconnect AC power,
pull the AGP card, put in the PCI, clear CMOS, then plug in
AC and try to POST again.  Try it at least 2 more times, as
it may reset the bios defaults to the lowest FSB at this
point if it had tried the CPU default previously (I don't
recall on that particular board, if it does this).

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After exhausting everything you/we/whoever can think of, all
that remains is swapping questionable parts into another
system or known good ones into that system.  Do try it with
the stripped-down config mentioned above, first.

If your PSU is generic or not rated for more than 180W on
the 3V+5V rails, then the PSU is another likely suspect.
Your board uses 5V rail for powering the CPU power
subcircuit, so it needs a fairly strong PSU 5V rating, even
moreso if your video card is power hungry but doesn't use
mostly 12V from an aux connector (some do, some don't, you'd
have to web search for your card's specifics if unsure).

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It shouldn't cost that much, there are still nForce2 boards
in the market for under $50, or an older design ATX 1.2/1.3
PSU for about the same.

If you are ambitious, you could also unplug your PSU from AC
for a few minutes then open and examine it- mostly checking
for failed capacitors, this is after you'd checked it with a
multimeter, since if the voltages aren't ok then it is more
clearly the problem... but further feedback on the issues I
pointed out earlier might help to pinpoint the problem.

Re: Failure to POST: mobo or power supply?

kony wrote:
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"seemed to struggle" meaning the mouse and menus would freeze and the
OS being un unusable.  The computer would boot and I would be able to
use the mouse and keyboard to login, but within a few seconds/minutes,
the screen would freeze.

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Video freezing meaning the mouse/keyboard would not be able to move
anything on the screen nor start/stop any process, and any current
desktop objects/windows would not move or animate anything, a complete

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You are right, I guess the system does POST, but the it's the video
that is not working.  The system starts up and through an audio warning
system that is part of the mobo, I know that the system is able to
boot, but it complains about the AGP slot.

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The AGP light which tells if the AGP card is correctly in place
initially goes on when I place it in, but immediately turns off
afterwards.  Everything else on the system seems to be working fine,
although I cannot completely verify this because I have no video.

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The monitor does detect that it is connected to a video card, but there
is no signal or video going to the monitor at any time.  It is in a
constant state of being on and idle (yellowish orange light, not

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The video card works in other computers I have swapped it into.  Other
video cards that work that I have swapped into this system does not
work.  The problem seems to be the AGP slot or the power that goes to
the AGP slot.

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All of that sounds like a lot of work that takes a lot of time.  I do
not have a multimeter and am not really intereseted in spending the
time swapping parts in and out.  Although clearing the CMOS sounds like
something worth trying.

Re: Failure to POST: mobo or power supply?

On 20 Sep 2006 07:40:22 -0700, "tofu.captain"

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What I was interested in, was whether the system can do
anything, anything at all while in the frozen video state.

For example, if music were playing, does it stop or stutter
or loop?  Does the system seem to respond to keyboard
commands to shut it down?

Video freezing is only part of the story, it is useful to
know the exact state of the system besides it having frozen
video, anything and everything you can think of to test

Also, when it freezes, can you push the reset button (if the
case has one) to reset?  If not, will the power button turn
it off?  

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You are still not telling us exactly, as you observe it,
what happens.  I mean an exact play-by-play account.

I doubt it says "this is a complaint", for example.  What
exactly happens, what is this audio warning message saying

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Examine the AGP slot contacts, using a strong light if
possible.  Check to see if the motherboard is *centered*
over the motherboard tray mounting studs, perhaps it's
off-center just enough that given time it has failed to make
good contact due to a slight misalignment.  If the system
was in a dirty/dusty/smoky/etc environment, you might try
folding over a piece of paper soaked in contact cleaner,
slip that over the AGP card contacts and insert into the
slot a couple of times in an attemp to clean them... just
make sure the paper doesn't fall apart from being saturated
with the contact cleaner so it doesn't leave behind large
particles in the slot.  That is, unless you can see the
contacts very clearly and are sure they are pristine.

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That is not necessarily a detection that it is connected to
a video card, some monitors will do exactly this with no
card connected, or do you have further observations that you
particular monitor does something different when unplugged
such as displaying a test pattern or no-video message?

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Ok, this is very useful info.  What kind of functionality is
needed for this board?  I'd try a PCI card, and continue
using if it acceptible performance per the system purpose.


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Well yes, pinpointing a problem can take a long time, if the
first few more likely (or common) faults, aren't what's
wrong.   You still have yet to even itemize the system,
which is quite odd to omit in a hardware group with this
problem, but at this point it seems that if you need to use
an AGP video card, you should seek a new board, if yours
isn't under warranty by Asus anymore, but do try clearing
CMOS first- that is usually the very first thing to try.

Re: Failure to POST: mobo or power supply?

tofu.captain wrote:

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If youre not willing to swap parts I'm not sure theres that much one
can do to help. Fit an old pci vid card, remove agp card, clear CMOS
and if necessary set to default on bootup, and boot it with a dos
floppy (eg win95/98 startup disc) to see if it'll run something.

Why a dos floppy? Often PCs will boot into DOS when they wont work with
win, and its a quick easy basic function check.

If this fails, give it to someone willing to sort it.


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