Help--homebuilt computer stopped working

I built my son a computer last May, using an Asus IS7 mobo and P4/2.8. For
Christmas I got him new memory, so it's now running 1 GB Dual-channel DDR400
as two sticks of 512.

Sometime overnight the computer stopped working. It was idling unattended
at the time; he was down the street at a New Year's party. When we hit the
power switch, the case and processor fans start running and LEDs come on,
but there is no signal to the monitor and the USB Microsoft Optical Wheel
Mouse doesn't light. There are NO beeps.

I removed and reseated the DVD burner, memory and processor (and replaced
the heatsink putty) with no change whatever.

The only physical symptom is that the fan over the Northbridge chip is
running at irregular speed, as if a bearing were going bad. This is the
first computer I've seen that even had a fan over the Northbridge, but I'm
assuming, since it's there, it must be needed.

Any suggestions?

Thanks,
--
P.

On Sun, 01 Jan 2006 20:23:52 +0000, Pelysma thoughtfully wrote:

I built my son a computer last May, using an Asus IS7 mobo and P4/2.8.
For Christmas I got him new memory, so it's now running 1 GB Dual-channel
DDR400 as two sticks of 512.

Sometime overnight the computer stopped working. It was idling unattended
at the time; he was down the street at a New Year's party. When we hit
the power switch, the case and processor fans start running and LEDs come
on, but there is no signal to the monitor and the USB Microsoft Optical
Wheel Mouse doesn't light. There are NO beeps.

I removed and reseated the DVD burner, memory and processor (and replaced
the heatsink putty) with no change whatever.

The only physical symptom is that the fan over the Northbridge chip is
running at irregular speed, as if a bearing were going bad. This is the
first computer I've seen that even had a fan over the Northbridge, but I'm
assuming, since it's there, it must be needed.

Any suggestions?

Thanks,

psu ?

"jaster" wrote in message
t...
On Sun, 01 Jan 2006 20:23:52 +0000, Pelysma thoughtfully wrote:

I built my son a computer last May, using an Asus IS7 mobo and P4/2.8.
For Christmas I got him new memory, so it's now running 1 GB Dual-channel
DDR400 as two sticks of 512.

Sometime overnight the computer stopped working. It was idling
unattended
at the time; he was down the street at a New Year's party. When we hit
the power switch, the case and processor fans start running and LEDs come
on, but there is no signal to the monitor and the USB Microsoft Optical
Wheel Mouse doesn't light. There are NO beeps.

I removed and reseated the DVD burner, memory and processor (and replaced
the heatsink putty) with no change whatever.

The only physical symptom is that the fan over the Northbridge chip is
running at irregular speed, as if a bearing were going bad. This is the
first computer I've seen that even had a fan over the Northbridge, but
I'm
assuming, since it's there, it must be needed.

Any suggestions?

Thanks,

psu ?

Not unless one of the 12v supplementary wires just blinked out. Are there
fuses in there?

Since things light up and fans run, the psu isn't completely dead. I will
find a way to test the four-conductor line that goes to the CPU, though.
Unfortunately, I don't have a meter close at hand, but it's worth checking
out.

Thanks,
--
P.

Apparently your motherboard has died. Time for a replacement.

--
DaveW

----------------
"Pelysma" wrote in message
news:sTWtf.42$cN4.10@trnddc07...
I built my son a computer last May, using an Asus IS7 mobo and P4/2.8. For
Christmas I got him new memory, so it's now running 1 GB Dual-channel
DDR400 as two sticks of 512.

Sometime overnight the computer stopped working. It was idling unattended
at the time; he was down the street at a New Year's party. When we hit
the power switch, the case and processor fans start running and LEDs come
on, but there is no signal to the monitor and the USB Microsoft Optical
Wheel Mouse doesn't light. There are NO beeps.

I removed and reseated the DVD burner, memory and processor (and replaced
the heatsink putty) with no change whatever.

The only physical symptom is that the fan over the Northbridge chip is
running at irregular speed, as if a bearing were going bad. This is the
first computer I've seen that even had a fan over the Northbridge, but I'm
assuming, since it's there, it must be needed.

Any suggestions?

Thanks,
--
P.

Pelysma wrote:
I built my son a computer last May, using an Asus IS7 mobo and P4/2.8. For
Christmas I got him new memory, so it's now running 1 GB Dual-channel DDR400
as two sticks of 512.

Sometime overnight the computer stopped working. It was idling unattended
at the time; he was down the street at a New Year's party. When we hit the
power switch, the case and processor fans start running and LEDs come on,
but there is no signal to the monitor and the USB Microsoft Optical Wheel
Mouse doesn't light. There are NO beeps.

I removed and reseated the DVD burner, memory and processor (and replaced
the heatsink putty) with no change whatever.

The only physical symptom is that the fan over the Northbridge chip is
running at irregular speed, as if a bearing were going bad.

Is it possible that the mobo was very, very shorted all along, and
installing the new memory shifted it around just enough to finally make
the short really bad? This can happen around the mounting points and
at the corners.

I've found that even tiny, insignificant changes in voltage can cause
audible changes in fan noise. Still, I would first try another power
supply or measure the voltages coming out of the one in there now with
a digital multimeter. Any cheapo $3-15 meter is more than accurate
enough, provided that it's digital. Sometimes a PSU will work
partially and put out only some of its three main voltages That
happened to mine after a friend plugged a DIMM in backwards and blew
the +3.3V rail.

Also try measuring the CPU, memory, and AGP power voltages, although
that requires finding the transistors or chips that have those voltages
on them. The AGP and memory voltage regulators are near their
respective devices and are probably 3-terminal chips (2-3 pins on one
side and a metal tab on the other). The CPU voltage regulator is the
big one, usually with 1-3 donut coils, several cylindrical capacitors,
and anywhere from 2-6 MOSFETs. The CPU voltage is on the metal tab of
at least one of those MOSFETs. Don't let your meter probe slip and
short something.

"larry moe 'n curly" wrote in message
oups.com...

Is it possible that the mobo was very, very shorted all along, and
installing the new memory shifted it around just enough to finally make
the short really bad? This can happen around the mounting points and
at the corners.


I want to thank you for your comprehensive answer. Unfortunately, I don't
have a meter in the house at the moment, and I'm going to have to rustle one
up; I guess this is a good excuse to finally invest in one. Previously, as
a community college student, I used the ones in the labs.

Three possibilities present themselves: the Northbridge fan isn't good, so
that chipset might have fried; the PSU, which is ample (450 watts) and not
very old, nevertheless might have stopped delivering 12v to the additional
4-conductor connector for the P4 CPU; and fan sensors might have told the
BIOS to shut down. I also want to try putting his original single DIMM
back in, but it makes me cry because that one is running in my Dell at the
moment, and I'll have to shut down the family machine to experiment with my
son's game machine.

I strongly doubt that the mobo is shorted at the mounting points; I put it
in myself, and used quite a lot of care and some nice little nylon washers
to minimize that possibility. However, it's worth looking it over.

Thanks again for taking the time to answer.

--
P.

Pelysma wrote:
"larry moe 'n curly" wrote in message
oups.com...

Three possibilities present themselves: the Northbridge fan isn't good, so
that chipset might have fried; the PSU, which is ample (450 watts) and not
very old, nevertheless might have stopped delivering 12v to the additional
4-conductor connector for the P4 CPU; and fan sensors might have told the
BIOS to shut down. I also want to try putting his original single DIMM
back in, but it makes me cry because that one is running in my Dell at the
moment, and I'll have to shut down the family machine to experiment with my
son's game machine.

I strongly doubt that the mobo is shorted at the mounting points; I put it
in myself, and used quite a lot of care and some nice little nylon washers
to minimize that possibility. However, it's worth looking it over.

Did you install the washers on both top and bottom of each hole? Also
I've found that mobos and cases can flex a lot, sometimes enough to
touch one another, so I make it a point to support the mobo within 1"
of each corner, even if that means attaching stick-on rubber feet to
the case.

My guess is that if the northbridge has a substantial heatsink on it in
addition to the fan, it didn't fry but could have let the chip get hot
enough to make operation unreliable. A have a budget Asus (Asrock)
with a fanless northbridge, but the heatsink extends about 1.5" above
the chip.

What kind of 450W PSU is it? Because if it looks more like this:

http://static.flickr.com/43/73954319_bc8f9de6d0.jpg

rather than this:

http://static.flickr.com/28/67715167_9880b9e1c4.jpg

then it can't be trusted, even though your son's computer probably
draws only 200-250W. One expert damaged two 500W Powmax Assassin PSUs
at loads of just 265W and 277W, but he managed to get 500W out of a
Fortron-Source (AKA Sparkle, Hi-Q, PowerQ) rated for just 300W. BTW
the PSU in the first link is rated for 580W, the second one for 200W --
that's how much PSU quality varies.

"larry moe 'n curly" wrote in message
oups.com...

Pelysma wrote:
"larry moe 'n curly" wrote in message
oups.com...

Three possibilities present themselves: the Northbridge fan isn't good,
so
that chipset might have fried; the PSU, which is ample (450 watts) and
not
very old, nevertheless might have stopped delivering 12v to the
additional
4-conductor connector for the P4 CPU; and fan sensors might have told
the
BIOS to shut down. I also want to try putting his original single DIMM
back in, but it makes me cry because that one is running in my Dell at
the
moment, and I'll have to shut down the family machine to experiment with
my
son's game machine.

I strongly doubt that the mobo is shorted at the mounting points; I put
it
in myself, and used quite a lot of care and some nice little nylon
washers
to minimize that possibility. However, it's worth looking it over.

Did you install the washers on both top and bottom of each hole? Also
I've found that mobos and cases can flex a lot, sometimes enough to
touch one another, so I make it a point to support the mobo within 1"
of each corner, even if that means attaching stick-on rubber feet to
the case.

My guess is that if the northbridge has a substantial heatsink on it in
addition to the fan, it didn't fry but could have let the chip get hot
enough to make operation unreliable. A have a budget Asus (Asrock)
with a fanless northbridge, but the heatsink extends about 1.5" above
the chip.

What kind of 450W PSU is it? Because if it looks more like this:

http://static.flickr.com/43/73954319_bc8f9de6d0.jpg

rather than this:

http://static.flickr.com/28/67715167_9880b9e1c4.jpg

then it can't be trusted, even though your son's computer probably
draws only 200-250W. One expert damaged two 500W Powmax Assassin PSUs
at loads of just 265W and 277W, but he managed to get 500W out of a
Fortron-Source (AKA Sparkle, Hi-Q, PowerQ) rated for just 300W. BTW
the PSU in the first link is rated for 580W, the second one for 200W --
that's how much PSU quality varies.


Well, it looks more like the second than the first, but I also made an error
earlier: it's 350w, not 450w, as I ended up using the Antec psu that came
with the case instead of buying the one I was looking at. Might have to go
back and get it now...

But I can't find a dead wire, either. The voltages on the PSU cables
themselves are as advertised. The MOSFETs you mentioned are as follows:
Two at bottom end of RAM slots, 3.28v each; one at corner of PCI bus, 2.38v;
one next to AGP slot, 1.06v; two next to CPU, 1.17v each.

The memory sticks work in my Dell (this one) but I haven't had the guts to
try the CPU; don't even know if it has the same number of pins. Messing
that deeply with the best working computer in the house when I seem to have
fritzed one out is a scary thought.

Thanks for your input.

--
P.

Pelysma wrote:
The voltages on the PSU cables themselves are as advertised.
The MOSFETs you mentioned are as follows: Two at bottom end
of RAM slots, 3.28v each; one at corner of PCI bus, 2.38v; one
next to AGP slot, 1.06v; two next to CPU, 1.17v each.

The memory sticks work in my Dell (this one) but I haven't had the guts to
try the CPU; don't even know if it has the same number of pins.

I hate to say it, but I'm afraid your initial diagnosis of a fried
north bridge is correct. This is why I don't trust fans, especially
the really small ones, which seem to fail the most. On any replacement
mobo,. I'd replace any north bridge fan with a heatsink large enough to
keep that chip from frying even in case of fan failure.

"larry moe 'n curly" wrote in message
oups.com...

Pelysma wrote:
The voltages on the PSU cables themselves are as advertised.
The MOSFETs you mentioned are as follows: Two at bottom end
of RAM slots, 3.28v each; one at corner of PCI bus, 2.38v; one
next to AGP slot, 1.06v; two next to CPU, 1.17v each.

The memory sticks work in my Dell (this one) but I haven't had the guts
to
try the CPU; don't even know if it has the same number of pins.

I hate to say it, but I'm afraid your initial diagnosis of a fried
north bridge is correct. This is why I don't trust fans, especially
the really small ones, which seem to fail the most. On any replacement
mobo,. I'd replace any north bridge fan with a heatsink large enough to
keep that chip from frying even in case of fan failure.


Well, we're just about out of the woods here. I replaced the motherboard
with an Asus P4P800-VM, and it POSTs. As I write this, I'm in the last
stages of hooking things up.

I think I've found the problem on the Abit board, too. There's a visible
blister on a small standing capacitor right next to the BIOS chip. Without
really knowing, that seems to make perfect sense. He plays a game online
called Pop-Cap all the time...

--
P.