Motherboard doesn't power up

  • Thread starter Thread starter amitupadhyay
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amitupadhyay

Hi,
i recently got replaced my Asus A7N266-VM motherboard with A7V400-MX
after the previous one stopped working.
I've put all the things in place according to the user manual. But when
i power up my system (i.e. before even pressing the start button on the
front panel) the LED on the motherboard lights up (which is ok) but
simultaneously the CPU fan the chassis fan start running(!!).
After about 10 seconds the fans stop running and then pressing the
start button doesn't do anything. I am not even able to hear the beeps
to see if there could be some problem.
Any ideas where the problem could be? i've checked the power connectors
- those are properly connected.

Thanks.
 
Hi,
i recently got replaced my Asus A7N266-VM motherboard with A7V400-MX
after the previous one stopped working.
I've put all the things in place according to the user manual. But when
i power up my system (i.e. before even pressing the start button on the
front panel) the LED on the motherboard lights up (which is ok) but
simultaneously the CPU fan the chassis fan start running(!!).
After about 10 seconds the fans stop running and then pressing the
start button doesn't do anything. I am not even able to hear the beeps
to see if there could be some problem.
Any ideas where the problem could be? i've checked the power connectors
- those are properly connected.
Click to expand...



How do you know the original board was bad?
It might have been another problem such as the power supply etc
 
How do you know the original board was bad?
It might have been another problem such as the power supply etc
Click to expand...

I took my system to the service centre. They found that the problem was
with the m.board and they provided me with a replacement motherboard.

Anyways, as of now my main problem is why the hell does the fan starts
running ( for sometime) when i've not pressed the power button. Also
i've noticed that the LEDs on the keyboard and the CD Drive also light
up momentarily just as the fans start running.

This is confusing because i've read (and tested) that the power supply
doesn't power up until the motherboard is started by pressing the power
button - so why is the fan getting that momentary power supply before
the start button is pressed.
 
I have an Intel motherboard that will power up as you describe whenever
power is initially applied. It then shuts back down and works normally.

All I might suggest would be to unplug the power cable for a while and maybe
the power supply will reset.

Do you know if the replacement was new? Recheck all your connections and
things like which connector do you have any CPU fan connect to.

Clark
 
The motheboard is new and when I got from the service centre I saw that
it was
working there.
I have also checked with a working ATX power supply from another
computer -
but the problem is still there. It just powers up and then everything
stops. The power
button wont work.

One thing i noticed recently is that if I keep pressing the power
button for a few seconds
(as we do when we want to normally shutdown the computer) then release
it - and then
if I press it the fan starts for a few seconds again.
The momentary fan start doesn't work if I just press the power button
and then release
it immediately.
Does this point to anything?
 
I took my system to the service centre. They found that the problem was
with the m.board and they provided me with a replacement motherboard.
Click to expand...

Did they provide any detail of how, what evidence led to
their diagnosis? Is this system under some warranty, since
it was at a "service center"?

In an ideal world one would hope service centers can
pinpoint and solve these types of problems, but personally I
don't put too much confidence in them, and perhaps rightly
so as well trained technicians putting a lot of time into
one system would soon negate more than the profit margin.

Did they have the entire system reassembled and then shown
to be working properly? One can take a board, put it on an
testbed and prove it working, but then later after
disassembling the testbed, handing and installing the board
in the other system, potentially cause a problem such that
the board is no longer "working"... it is less likely, but
"IF" the power supply isn't the problem I would refocus on
the motherboard.


It would be good to have started the thread with a concise
but complete list of all major system components. For all
we know you might just have PC2100 memory that the board is
trying to run at higher speed. One thing to try if you
hadn't already, is clearing the CMOS (while AC power is
disconnected). Another is to remove all but the bare
essential parts- CPU, 1 memory module, and video (which is
possibly integrated onto the board?). Disconnect other
cards, drives, etc, from both the board and power.

Anyways, as of now my main problem is why the hell does the fan starts
running ( for sometime) when i've not pressed the power button. Also
i've noticed that the LEDs on the keyboard and the CD Drive also light
up momentarily just as the fans start running.
Click to expand...

The first time AC power is restored to the PSU, some boards
will do this... and in those cases it can be ignored because
the next time the board will behave typically and not do
this.
This is confusing because i've read (and tested) that the power supply
doesn't power up until the motherboard is started by pressing the power
button - so why is the fan getting that momentary power supply before
the start button is pressed.
Click to expand...

Sometimes they do, the board momentarily turns the PSU on
and off again.
 
Did they provide any detail of how, what evidence led to
their diagnosis? No.
Is this system under some warranty, since
it was at a "service center"?
Click to expand...
Yes the system was under a warranty that is why they replaced it.
Did they have the entire system reassembled and then shown
to be working properly? One can take a board, put it on an
testbed and prove it working
Click to expand...
This is exactly what they did (used a testbed), seems like i'll have to
take my system over there.
One thing to try if you hadn't already, is clearing the CMOS (while AC power is
disconnected). Another is to remove all but the bare
essential parts- CPU, 1 memory module, and video (which is
possibly integrated onto the board?).
Click to expand...
I've tried both these things. Clearing the CMOS did help in one way
that when i cleared it for the first time, the fan did not start
automatically on powering up (I thought it would work this time) but
then again nothing happened.
 
Did you make sure your video card is seated and everything else. Sometime
you can miss little problems, and the longer you look, the harder it is to
see. Have you reseated the CPU and made sure it had heat sink compound on
it. Maybe even loosen some of the screws holding the motherboard in to
relieve any stress. Have you rechecked the connections to the LEDs and
reset switch and power switch. They can be confusing sometimes and on some
the polarity makes a difference.

Take everything out you don't need to boot and see if it will. If it keeps
having problems, and you know all the connections are correct, I would try
to get another one.

Clark
 
Amit wrote:
Yes the system was under a warranty that is why they replaced it.
Click to expand...

I wonder if they'll be paid for labor on this by the mobo maker. If
not, then at least they're probably honest.

Some mobo BIOSes have a setting for automatically turning on after
power failure. Maybe yours makes its CMOS default to this. OTOH some
PSUs will blip on for a fraction of a second when they're plugged into
the AC.

Have you checked the power button to see that its wiring is good, is
connected to the correct two pins on the mobo, and that the switch
contacts are working properly? What happens when you try to turn on
the computer by momentarily shorting the two power-on pins on the mobo?

Is it possible that your mobo is shorting out against your case? Did
you test the mobo outside of the case while it was sitting on either
anti-static foam sheet or standoffs? A lot of people say mobos are now
designed so they won't short at the mounting holes even when no
insulating washers are used, but I still find exceptions. Also is your
mobo well-supported close to its corners? Because I've seen
unsupported mobos short to the case, and cases flex a lot more than
you'd expect. So I put a standoff in every hole, even if there's no
matching hole in the case (sometimes you need different length
standoffs because of this), or at least I put stick-on rubber bumper
feet on the mobo tray.
 
Thanks guys.
Just to update - my system is working fine now. I took it to the
services centre again - this time with the whole case, my processor,
RAM and PSU etc. When they assembled it there it had the same problem.
Then I don't really know what they did ... (probably there was some
loose connection somewhere) but it started working when they tested
with a different processor and RAM.
Then they plugged in my processor and it was working fine.
 
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