Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <3a62719kvcbubdt1gs40eo7a11ro650td9@4ax.com>, Jerry
<jerry@remove.veridian.fsworld.co.uk> wrote:
> On Thu, 28 Apr 2005 11:22:48 -0400, nospam@needed.com (Paul) wrote:
>
> >In article <gbr171dm6nlqaihh3am58vrjo36stb5dl6@4ax.com>, Jerry
> ><jerry@remove.veridian.fsworld.co.uk> wrote:
> >
> >> Just replaced an Abit m/b which had mouse communication probs.
> >>
> >> When I fire it up absolutely nothing happens. However, I have the
> >> green LED lit up.
> >>
> >> Other than that there is no activity at all. LED on from of box seem
> >> to be dead too although they may be dependent upon the box on/off
> >> switch being OK.
> >>
> >> Tried clearing CMOS. I'm lost now. Can someone help or is the M/B
> >> DOA?
> >>
> >> I have the Mem, graphics card (ATI 8600) and a HD in place BTW.
> >>
> >
> >Is the power switch connected to the correct two pins ?
> >
> >You don't have to connect everything up on the PANEL
> >header if you don't want. Connecting just the power
> >switch to its two pins, is enough to get things started.
> >You won't hear any beeps from the PC speaker, but if the
> >computer starts, maybe you won't need to listen to the
> >beeps.
> >
> > Paul
>
> Thnx for your input
>
> Tried the power switch, checked it, even reversed polarity (although I
> don't think that matter). Nothing!
>
> Funnily enough a) I've just put a 939 Asus board in another machine -
> worked like a dream and b) apart from the mouse issue the "old" board
> worked fine.
Seeing the green LED on the motherboard, means the motherboard
is getting +5VSB. That is the only voltage that shows up
initially when you switch on, via the switch on the back of
the computer. One of the purposes of the green LED, is you
should not add or remove hardware components if the green LED
is lit.
The power switch goes to two pins on the PANEL connector. A
momentary contact on the switch, should be latched by a chip on
the motherboard. In turn, that drives the PS_ON# signal on the
ATX 20 pin power connector to a logic 0, which is supposed to
turn on the PSU. You have indicated neither a "twitch of the
fans" nor a short powered up interval after trying the power
button, so that means that the normal sequence of events has
been interrupted.
Some Asus boards have a circuit called AGP_warn. It is located
next to the AGP slot. In recent months, it looks like Asus has
been removing the components from that circuit, so they might
not be using it any more. What that circuit used to do, is if
a mis-keyed 3.3V only AGP card was stuffed in the AGP slot,
the motherboard would be prevented from powering up. Pretty
well your exact symptoms.
To test for that, you could try removing the AGP card, and
see if the system will power up. (A board should be able to
start without a video card connected, and you should get the
beep code that says the video card is missing.)
I think the next step for you, is to assemble the system
outside your computer case. That is referred to as the
"cardboard" test, because you rest the motherboard on
an insulator while testing. (I like to use a thick phone
book.) If the motherboard will start that way, then something
must have been shorting.
In terms of power connectors, there is only the main 20 pin ATX
power connector, so it doesn't look like any other power cable
is missing.
You might try disconnecting the reset switch. I'm not
really sure whether reset prevents the power switch from
working or not. If reset was stuck in the "ON" position,
the board would not POST, but I would think the PS_ON#
logic would likely still work. (Hardware designers normally
design a reset signal, so it overrides all other logic,
but motherboard designers don't seem to follow this
practice. My A7N8X-E for example, can get wedged in states
where the reset button won't do anything.)
The motherboard should have been functionally tested
at the factory. Unless this is a refurb, or the board
has been subjected to stresses while being shipped,
it really should work.
Tell me, has the PSU ever been tested with another
motherboard ? Do you know that the PSU is actually
capable of turning on ? Perhaps you could test the
new PSU on another computer. An alternative, is to
test it by connecting PS_ON# to an adjacent COM signal,
on the 20 pin connector (I don't like recommending this
to people, so my preference would be to have tested
the PSU on another motherboard. While there should be
no dire consequences from connecting PS_ON# to GND,
I don't have a guarantee in writing that such a thing
is completely safe to do. I use dummy resistor loads
on my PSU when operating the PSU manually like that.)
If the PSU has a 115/220 selector switch on it, check
to make sure it is in the correct position. If the PSU
has such a selector switch, don't play with it while the
PSU is plugged in! In fact, you should always unplug
the power, before working in the case. (One poster here
actually had a PSU that continued to run, after the
switch on the back of the computer was switched off.
Unplugging is the only way to guarantee there is
no power present.)
HTH,
Paul
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