A7N8X, won't start, nothing happens

  • Thread starter Thread starter Tyler Porter
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T

Tyler Porter

Ive had this setup for about 9 months now, been working perfectly. I
started having some freezing problems the other day. It locked up, I
rebooted, it locked up again, rebooted again, and then as it was
starting It sounded normal, POST responded with all clear, but there
was no image on the monitor. I tried adjusting the monitor cable,
thinking it was coming loose, and the computer switched itself off.
Since then, it has refused to respond at all to the power on switch.
When the power supply is switched on, the two LEDs on the board itself
power up, and the front lighted bezel of my case comes on. But
hitting the power switch causes nothing to happen. I have tested the
power supply on another board, and it booted up fine. I also tested
the power switch itself, also booted fine. I have removed everything
from the case to check for shorts, still nothing. Ive reseated or
removed components (including video card.) Reset the bios, nothing.
removed the memory to try to force a beep code, still nothing. It
simply does nothing, none of the fans come on (including PSU) nor do
any of the HDs spin up.

Im totally at a loss here. Thanks for the help guys.

Setup:
Antec 350w PSU
Asus A7N8X deluxe
Athlon XP 2400+
two 512meg Corsair XMS2700 DDR ram chips
2 IBM 7200rpm HDs, 20 gig and 80gig
Yamaha 52x burner
Gainward geforce 4 4800 se
ATI TV tuner
Linksys wireless G access card
 
PSU has been enough for the last 9 months, its been working fine with
exactly this setup. Plus a friend has the same PSU and almost the same
stuff, works perfect.

I dont see how it could be overheating if it doesnt start in the first
place. And I know it didnt overheat to cause the problem originally, as my
case has a thermometer readout right on the front, and it was running
normally, as thats the first thing I check.
 
Tyler Porter said:
PSU has been enough for the last 9 months, its been working fine with
exactly this setup. Plus a friend has the same PSU and almost the same
stuff, works perfect.

I dont see how it could be overheating if it doesnt start in the first
place. And I know it didnt overheat to cause the problem originally, as my
case has a thermometer readout right on the front, and it was running
normally, as thats the first thing I check.
Click to expand...
Ever heard of component failure?
How do you know the PSU hasn't failed? As you have a friend with the "same
PSU", swap them and see what happens.
I not *sure* your PSU is bad, but until you do some objective testing, you
know nothing.
 
The two LEDS on the board should not light up, only the green one should as
that shows power.
The red one should always be off as that warns of the wrong type(voltage)agp
card or if the card is not fitted correctly.
With 1.5v card the red LED stays off(if 1.5v card is correctly installed),
with an older card that uses any other voltage then the red LED stays on and
will stop power to the card.
The Red LED cannot be/should not be on if a 1.5v card is used(and installed
correctly).
 
I did objective testing of the PSU, and stated that in the original post. I
took the PSU from this computer, and hooked it up to another computer. that
computer booted up perfectly. I also took another power supply that I know
is good, as I was using it in another computer before and after the test
with perfect results. I attached that PSU to this motherboard, and got the
same problem, it wouldnt respond at all to the ATX power on switch. Before
getting angry maybe you should read the post.
 
My A7N8X (rev 1.04) did nearly the same thing. One day fine, the next day
phhhht! RMA'd it back to Newegg, and got a nice, new rev 2.0 back which is
running nicely. Methinks the BIOS on these boards is sooooo touchy that I no
longer 'experiment' with O/C settings; all is stock, and that's the way it
stays!
 
My A7N8X (rev 1.04) did nearly the same thing. One day fine, the next day
phhhht! RMA'd it back to Newegg, and got a nice, new rev 2.0 back which is
running nicely. Methinks the BIOS on these boards is sooooo touchy that I no
longer 'experiment' with O/C settings; all is stock, and that's the way it
stays!
Click to expand...

Is that a Deluxe or a non-dlx? I've changed & saved the BIOS settings
probably 200 times on my A7N8X v2(non-dlx), no problems yet, be 8 months
old in about another week.

Ed
 
hmm, that light is on, even when the vid card is installed. It may have
slipped a bit when I adjusted the monitor cable, could that have fried the
video card? I know the card WAS good, because ive been using it for 9
months. But maybe thats what died? However, wouldnt the mobo still start
up or give some sign of life with the video card removed? it does nothing
now, PSU fans dont even activate, whether the card is installed or not.
 
In the manual it says,
Red AGP warning LED. Serving as a smart burn-out protection the red LED
on the mother board lights up if you plug in any 3.3V AGP card into the
AGP slot.

BUT it also says,,,, When this LED is lit, there is no way you can turn
on the system power.

I'm no expert but it's starting to sound like your mobo bit the dust,
how can the red LED be lite if there is no card installed, doesn't sound
good.

Good luck,
Ed
 
Tyler,

I think your on the right track with the Vid card. Hopefully a re-seat
will cure it. When the PC starts up the first thing on the screen is
the BIOS information from the vid card, before any type of CPU/Board
data is displayed!! Not to say the board is OK but you ought to test it
with a known good video card first. As you stated in your initial post,
you lost video first before rebooting to complete loss! Keep us posted.

Rob
 
Yeah, its sounding like the video card might be it. Unfortunatly I dont
have a spare good video card to test it at the moment.

What im wondering is shouldnt the board start without a video card? It will
of course give an error code, but shouldnt it at least show some sign of
life? As it is right now the red AGP light is on when there is no video
card installed. Is that supposed to be on in that circumstance? Or is that
proving that there is something wrong with the board, possibly along with
the video card.
 
"Tyler Porter" said:
hmm, that light is on, even when the vid card is installed. It may have
slipped a bit when I adjusted the monitor cable, could that have fried the
video card? I know the card WAS good, because ive been using it for 9
months. But maybe thats what died? However, wouldnt the mobo still start
up or give some sign of life with the video card removed? it does nothing
now, PSU fans dont even activate, whether the card is installed or not.
Click to expand...

The red LED is "AGP warn" and is supposed to detect a video card
attempting to use or request 3.3V I/O. The AGP Warn circuit gates
the PS_ON# signal, so it will prevent all power with the exception
of +5VSB from being applied to the board. Either there is a pin bent
inside the AGP slot, or more likely that stupid little circuit is
just screwing up on its own. There have been other motherboards with
dead AGP Warn circuits on them, so this is not unheard of. Some
boards arrive from Asus with the red LED lighting on its own. Since
it is a simple minded (two transistor?) circuit, no amount of BIOS
flashing/CMOS clearing/praying to the gods will bring it back.

I just got out the ohmmeter and did some tracing. There are two
transistors, but to my surprise, they aren't cascaded. It looks
like the two transistors are fed from the same source, implying
that two functions occur in tandem. The transistors have no code
on them, so I have no idea if they are PNP/NPN or what their
B/C/E pins are. This is what I've traced so far.

+3.3V
|
-----
|10K| (1 of 4 in quad pak)
-----
--- | --- P/O AGP Warn circuit
--| | +-----| | as seen on Asus P4B
| |----/ | |-- motherboard rev 1.05
--| | | --| | (rev less than 1.05
--- | --- don't have this cct)
|
TYPEDET# (A2)

When a 1.5V AGP card is inserted, that pulls TYPEDET# to logic 0.
It also grounds the 10K resistor. There is more to this circuit,
but Paul's eyes are killing him...

My guess is one transistor is used to control the LED and the
other one messes with the logic path used for PS_ON#. At least
now my curiosity is satisfied that the circuit depends on TYPEDET#.
Not that this changes your need to RMA or anything :-(

The next step would be to measure voltages on the pins when the
circuit is "working".

If for any reason pin A2 of your video card (end closest to case and
closest to processor side) is not making contact, that would be enough
to leave TYPEDET# floating. When the video card is inserted, pin
A2 should be grounded by the video card, in order to extinguish the
LED and make the board power up via PS_ON#.

HTH,
Paul
 
Tyler Porter said:
I did objective testing of the PSU, and stated that in the original post. I
took the PSU from this computer, and hooked it up to another computer. that
computer booted up perfectly. I also took another power supply that I know
is good, as I was using it in another computer before and after the test
with perfect results. I attached that PSU to this motherboard, and got the
same problem, it wouldnt respond at all to the ATX power on switch. Before
getting angry maybe you should read the post.
Click to expand...
Mea culpa. I missed that line in the original.
 
Yeah, its sounding like the video card might be it. Unfortunatly I dont
have a spare good video card to test it at the moment.

What im wondering is shouldnt the board start without a video card? It will
of course give an error code, but shouldnt it at least show some sign of
life? As it is right now the red AGP light is on when there is no video
card installed. Is that supposed to be on in that circumstance? Or is that
proving that there is something wrong with the board, possibly along with
the video card.
Click to expand...

Well it's not like the mobo only works with AGP cards right?, you could
plug in a PCI video card and the red LED should stay off since all it's
supposed to do is detect 3.3 AGP cards. I'd bet you video card is fine
since the board acts the same with it installed or not.

Ed
 
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