spontaneous PC power losses - HELP!

[[email protected]]

I recently installed a DVD drive into my PC. (2 days ago.) Since then,
I get spontaneous power loss periodically - sometimes seconds after
booting, other times after hours of operation. I've tried replacing
the power supply, and I've tried removing all my hardware (other than
RAM), so I'm thinking it must be motherboard related.

Interestingly, trying to turn the machine back on does nothing.
HOWEVER...if I physically unplug the PC, and leave it off for a few
seconds, I then *can* reboot it. Looking inside the case, I notice a
green LED. When this goes out (after unplugging) it signals that I can
now successfully reboot. If I try to reboot before the light goes out
(about a 2 second wait) the reboot fails. I'm assuming the LED is
showing power remaining on the motherboard due to capacitors. I don't
know if that's a hint towards a solution?

Also, when I reboot, most (but not all) of the time the bios has been
reset as well.

Now the questions I've got are:
1) Why? I've installed drives dozens of times, and never had anything
like this.
2) How do I fix it? Presumably a new motherboard will do the trick,
though I'd like to a) confirm that's the cause and b) fix the existing
MB, if at all possible. (Historically, every time I've tried to
replace a MB I've ended up having to replace the entire PC. Apparently
my skills don't lie in that direction!)

Is there any chance I can salvage this board? I have no idea if
replacing the onboard battery, flashing the bios, or any of these
arcane things will do anything to help, or if it's physically broken
and needs a part replaced? A electrician friend tells me he thinks a
capacitor may have gone, but looking at the MB, none of them appear to
be swollen or leaking.

thanks a lot! any advice is appreciated!

 

[[email protected]]

thanks a lot! any advice is appreciated!

After all that waffle and piffle, you never even once conidered removing the
fucking DVD drive. Right?

Wow, you're quick to jump to conclusions. If you read the post, you'll
notice that:

"...I've tried replacing the power supply, and I've tried removing all
my hardware (other than
RAM), so I'm thinking it must be motherboard related."

So yes, of course I removed the DVD drive. Logically, the first thing
to try...

 

[[email protected]]

\>I recently installed a DVD drive into my PC. (2 days ago.) Since then,


Unplug/replug all power and data connections. That way, the errant loose one
will be fixed and your problem will be resolved.

Thank you for the tip. I did this, but no luck.

A couple interesting new developments: one one occasion when it
wouldn't start, holding down the power button kept the PC on, for as
long as I held it. That made me wonder if it was the switch, but the
effect was never repeated. Another time it wouldn't start, and I
disconnected all the devices but the hard drive, and then it started.
Yet other times I have disconnected every single device, and the fan
won't even spin and try to start.

Strange...

Thank you! I appreciate the helpers among the trolls.

 

[Ian Jackson]

I had a similar thing which drove me crazy. Happened just after fitting a
new graphics card. Which was just coincidence.
Turned out to be the main processor overheating and shutting down. Its
fan was working normally and no error messages generated. Removing the
heatsink, cleaning and applying new thermo conductive paste sorted it. Now
have a spare power supply...

I had the same problem with the PC shutting down when the processor was
working hard. Its heatsink was full of dust. Soon afterwards, I again
had shutdowns. This time it was because the PSU fan had seized solid
(probably dry bearings). Freeing-off and re-lubrication with WD40 has
worked for the last 6 months (but I will fit a new fan one day).

In the front of the case, I have since fitted an additional fan which
sucks the air in, and also blocked off some unused holes (to ensure that
most of the air entering passes through the fan). In front of the fan is
a crude filter made out of thin scouring pads. Every couple of weeks, I
wrench off the plastic front panel of the computer, and clean a VERY
dirty filter.

Finally, as this is an Asus motherboard, I have installed 'Asus PC
Probe' - a monitoring program which tells you things like the
temperature of the processor and hard drives, the voltage rails, the fan
speeds etc. As all is now working OK, I don't use it much, but it is
interesting to watch the processor rise from 28C to 45C during a
prolonged spell of 100% activity!

 

[Baron]

Thank you for the tip. I did this, but no luck.

A couple interesting new developments: one one occasion when it
wouldn't start, holding down the power button kept the PC on, for as
long as I held it. That made me wonder if it was the switch, but the
effect was never repeated. Another time it wouldn't start, and I
disconnected all the devices but the hard drive, and then it started.
Yet other times I have disconnected every single device, and the fan
won't even spin and try to start.

Strange...

Thank you! I appreciate the helpers among the trolls.

Clear the BIOS and then re-input the parameters.

 

[Bennett Price]

You didn't say how old the PC is. It might be the onboard battery.
First, try to reseat it; if that doesn't help, I'd try replacing it w.
a new one. Also, check carefully that the MB is not occasionally
shorting out to the chassis (that all insulating spacers are in place).

 

[Bennett Price]

You didn't say how old the PC is. It might be the onboard battery.
First, try to reseat it; if that doesn't help, I'd try replacing it w.
a new one. Also, check carefully that the MB is not occasionally
shorting out to the chassis (that all insulating spacers are in place).

 

[Ian Jackson]

Mine was relatively new and the heatsink clean. Plenty of fans, too, all
working. It's a home assembled one which worked fine for a year or so
before developing the symptoms. I used the paste which came with the
heatsink originally and that had gone hard - dunno why.

Unfortunately, in this house, there seems to be an inexhaustible supply
dirt and dust. God know where it comes from. You really would NOT
believe how filthy my home-made filter gets.

Actually, I forgot to mention also that the clamping of the heat
dissipater/ fan assembly to the processor was rather loose. This would
definitely have made things worse. I disassembled everything, cleaned
off the dust and thermal paste (which was still soft), did a bit of
judicious bending so the clamp was firm, put on new thermal paste, etc.
It was like a new machine when I had finished.

 

[Baron]

Mine was relatively new and the heatsink clean. Plenty of fans, too,
all working. It's a home assembled one which worked fine for a year or
so before developing the symptoms. I used the paste which came with
the heatsink originally and that had gone hard - dunno why.

The heat dries out most pastes ! That is why the move to phase change
materials was made. Also the phase change material allows for a much
thinner interface improving thermal conductivity and thus a more
effective heat transfer.