Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <3sUOc.1646$UN2.364@nwrddc02.gnilink.net>, "Vince"
<nospam@please.com> wrote:
> I have a BNIB A7N8X-E, I think it's DOA. No POST beep, no voice errors.
>
> How can I prove it's the mobo and not the CPU, memory, or video card?
>
> If I run the mobo without CPU, memory, or video, I still get no POST beep,
> but never having done this before I don't know if that's to be expected.
If you run the board without any components in it, the Voice POST
should tell you there is no CPU installed. You say you have +5VSB,
by the fact that the green LED on the motherboard is lit. When that
LED is lit, you should NOT be removing or adding components to the
computer. Turn off the computer at the back and unplug, before doing
any work. (The reason this is necessary, is one poster here had a
PSU that continued to work, even after the switch was set to OFF.
The PSU had a bad power switch. Unplugging ensures there is no way
for stray power to ruin something. If +5VSB is present when clearing
the CMOS, for example, you can burn a small dual diode in the CMOS
standby power path.)
Plug a set of amplified speakers into the lime colored, lineout jack
on the back of the computer. Turn on the power supply on the computer.
You can use the power switch on the front of the computer, or
momentarily touch a (ESD drained) screwdriver tip to the two power
switch pins on the PANEL header on the motherboard. Soon after
that, you should hear the Voice POST announce your CPU is missing.
There are probably a whole bunch of things that could stop it from
working. A couple I can think of:
A defective "AGP Warn" circuit will prevent the power switch
on the front of the computer case from working. I think pulling
the video card should disable that thing. Verify you are getting
the fans to spin, when you press the power switch on the front of
the computer. A lack of power could even be that the PSU isn't
listening to PS_ON#. You could verify the PSU works, by using it
on another computer.
Assuming the fans are spinning and you can hear the hard drive
spinning up, then for the Voice POST to not say anything, could
mean the reset circuit is not coming out of reset. All voltages
generated locally on the motherboard have to be stable before
the reset signal is deasserted, and the Voice POST can start.
The Voice POST should need very little to work - just the
presence of +5VSB (and you have the green LED to prove that is
there) plus a working reset signal. (If the reset switch on the
computer case is busted in the "stuck ON" state, that can ah heck
up the reset as well. Disconnect the reset switch from the
PANEL header to check that possibility.)
I'm told by another poster that he didn't even need the two jumpers
to be on the FP_AUDIO header, to be able to hear the Voice POST.
To be on the safe side, verify the jumpers are present and installed
properly anyway.
Before giving up on the motherboard, you should do the "cardboard
test". Place the motherboard on top of an insulator (I use a piece
of board). I lay the PSU and motherboard on a table top, and verify
piece by piece, adding components and listening to the Voice POST, to
see that it is getting past the detection stage for each one. By the
time you get to adding the keyboard and mouse, it can take up to a
minute after power is applied to the board, before the Voice POST
will tell you the keyboard is missing. (Use some ESD precautions,
such as touching the PSU case before inserting cards or CPUs etc.
Bring your body to ground potential, so no static leaps through you
and the pins on any components.)
If the board works on a piece of cardboard, then examine the case for
any means of shorting the board. If the screw heads on the standoffs
are too large, or are off center, they might be touching a component
or a live signal track. Also, only place standoffs where they line up
with screw holes on the motherboard. The screw holes on the motherboard
are plated and grounded on purpose, and are intended to come in contact
with the standoffs. Using a standoff where there is no hole, means it
can touch a signal track and short it.
Paul
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