PC powers up for a few seconds / minutes, but doesn't boot

pike_by_nature.DeleteThis@hotmail.com wrote:
> I suspect I already know what my problem is - but can anyone advise me
> on how to prove it?
>
> I often have to boot my PC up two or three times for it to boot
> properly. Usually, the red "hard disk" light comes on and stays on at
> boot up, and nothing else happens. I reboot once or twice, and it's as
> good as gold.
>
> Yesterday, the PC wouldn't boot. The monitor just remains blank. No
> ram counting, no "press delete to enter bios", no beeps, nothing. The
> fans come on, including the CPU fan and after a few seconds, it
> switches off. I switch it back on, and after a few minutes, it
> switches off. Still nothing. I've removed every peripheral going,
> taken out the ram (one chip at a time), removed and replaced the CPU
> (P4 2.. The CR2-32 battery is less than 12 months old - I replaced
> it last year suspecting it might be responsible for my boot-up
> problems.
>
> The motherboard is a Gigabyte GA-8IPE1000; so it's about three years
> old. I suspect it's lost the bios somehow. Can anyone offer any
> suggestions?
>
> TIA;
>
>
> Tim
>

What shape is the power supply in ? Maybe the power supply is switching
itself off. Maybe it isn't delivering the PWR_OK signal when it powers up.
Power supply failures are a common enough fault, that you could start
by swapping in a spare. Using a multimeter may tell you something, but
if it shuts off before you can examine all the pins on the main
connector, you may not get a complete picture.

You can contact the metal pins, while the connector is plugged into the
motherboard (from the back, where the wire enters the hole for each
pin). Pinout for 20 and 24 pins supplies can be found in these
specs. Using an alligator clip, and connecting the (-) lead to
an I/O connector screw, makes it easier to probe the machine with
the (+) lead, using one hand.

http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

If you don't own a multimeter, and don't want to check anything, just
try another power supply.

In the description, I don't see how the BIOS is responsible. If the
thing eventually boots, then there must have been BIOS code, and
it must have been spotless, to pass the checksum test early in the
POST sequence.

If this was purely a motherboard failure, about the only reason
for the motherboard deciding to turn things off, is if the CPU
overheated. Otherwise, if the processor doesn't boot or doesn't
appear to execute code, there is precious little reason for the
power to go off. So something has to help it. A bad power supply
can switch itself off if it wants. Software also knows how to
turn off a machine, but it has to run to work. Safety features,
like THERMTRIP (that is the CPU overheat protection) can do it.
But you've already been playing with the CPU, applied fresh
thermal paste, checked the clip, that the fan runs, and so on,
so it probably isn't overheat. I'd try another power supply.

Paul
 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot 

On Mon, 11 Jun 2007 01:32:27 -0700, pike_by_nature.TakeThisOut@hotmail.com wrote:

> Thanks Paul - yesterday, it wasn't booting at all. I never got as far
> as the Bios screen - that's what makes me wonder if the BIOS is
> responsible. I know that it's incredibly rare; and you're probably a
> lot closer with your thought re the power supply; I'll give that a go
> when I get home this evening - I've got a couple of spares laying
> around - and see what happens.
>
> Thanks again;
>
> Tim

Might want to also check the caps on the MB for bulging and leaking. If
your bios checks the fans, it's also possible there's a problem with a fan
speed being read properly. Bad video cards would also present this type
problem.

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 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot 

Hi Paul, Wes;

Changed the power supply - made no difference. I removed all the
peripherals; video card, ram and in the end, even the CPU; there is
now nothing attached to my motherboard but a power supply (and I've
done it with both), and it just powers up for a couple of seconds, and
powers down again. Very irritating.

Not sure what Wes meant by the "caps" on the motherboard - but there's
no obvious signs of burning or melting.


Tim
 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot 

Thanks Paul; I'll give it a go; but although last night it was
starting and dieing after 4 - 5 seconds, the day before, it was
starting, and going for 30 seconds to two minutes; without any boot
sequence or anything; just the lights on, fans whirring; nothing else,
and then shutting down. So while it's definitely worth a go, I suspect
the switch will prove to be okay.

(I'm coming round to the "it's trashed" theory again!)

Tim
 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot 

pike_by_nature.RemoveThis@hotmail.com wrote:
> Hi Paul, Wes;
>
> Changed the power supply - made no difference. I removed all the
> peripherals; video card, ram and in the end, even the CPU; there is
> now nothing attached to my motherboard but a power supply (and I've
> done it with both), and it just powers up for a couple of seconds, and
> powers down again. Very irritating.
>
> Not sure what Wes meant by the "caps" on the motherboard - but there's
> no obvious signs of burning or melting.
>
>
> Tim
>

Would the power switch be sticking in the "ON" state ?

Try connecting the reset switch to the two pins intended
for the power switch. That will allow you to use the
reset switch as a fake power switch, just for testing.
If it stays powered up, you could have a bad computer
case switch.

Wes is referring to electrolytic capacitors. They are the
aluminum cylinders with the plastic sleeves on them. Normally
the top of the cylinder is flat. If pressure builds up inside
them, the top bulges, and the pressure relief lines break.
Alternately, electrolyte leaks out the bottom of the capacitor,
and leaves a brown stain on the motherboard.

http://www.badcaps.net/images/caps/kt7/image004.png

When that happens, extra load is placed on the Vcore regulator
switching circuits. Some of them are equipped with overcurrent
detection. But I don't know if the symptoms in that case would
include shutting off the PC or not. From a hardware point of
view, it doesn't have to. The Vcore regulator chip can simply
shut itself off, and eventually the user will notice.

A visual inspection of the capacitors, will give you some idea
if this is a problem or not.

Paul
 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot 

On Tue, 12 Jun 2007 06:32:25 -0700, pike_by_nature.RemoveThis@hotmail.com wrote:

> Thanks Paul; I'll give it a go; but although last night it was
> starting and dieing after 4 - 5 seconds, the day before, it was
> starting, and going for 30 seconds to two minutes; without any boot
> sequence or anything; just the lights on, fans whirring; nothing else,
> and then shutting down. So while it's definitely worth a go, I suspect
> the switch will prove to be okay.
>
> (I'm coming round to the "it's trashed" theory again!)
>
> Tim

Paul explained the caps. The system won't boot without a cpu. So that
really doesn't test much, if anything. You have to have MB/CPU/ram/video
card to see anything of value. If you are never getting any video, then
connect the case speaker and see if you are getting any beeps. Different
beeps mean different things. If you're getting beeps, that will tell you
something.

--
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 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot 

Well, no bulging caps. I also swapped out the power and reset switches
- the fans come on, but nothing else (well, until they go off again,
which seems to be a variable time between 2 seconds and one minute -
very approximately). The internal speaker is connected, but I don't
get any beeps. The boot up sequence never even starts. The PC just
wakes up, but nothing else happens at all. I've now put back the CPU,
RAM, video card and hard disk - but I still don't get anywhere at
all.

Methinks I might get a quote from my local parts supplier for a P4
motherboard that will take my DDR 184 pin ram!


Tim
 >> Stay informed about: PC powers up for a few seconds / minutes, but doesn't boot