[solved] mainboard not POSTing after CPU cooler exchange

[fangorn]

Hi,

I know this is not a Gentoo problem, but I feel like a beginner right now.

I have halted my machine (Asus P6T, Core i7 920) to replace the CPU cooler by a more quiet one.

After the replacement the machine is dead. When starting the fans are spinning up, the DVD drive
and harddisk are starting normally. But the Nvidia graphics card shows nothing. And no beeping
signals a successfull or failed POST.

I redid all the cabeling, removed and reinstalled the CPU and its cooler, removed the board from
the case and put it on an isolated mat, reduced the parts to an absolute minimum.

Even without Graphics card and RAM nothing signals that the BIOS is testing the machine.
I removed the BIOS battery for minutes and the machine is still doing nothing.

The only thing different in the startup process is that when starting after a few seconds the
machine resets itself and boots again. After that it runs constantly without doing anything.

Every part of the machine worked perfectly before the power down.

I am completely out of ideas right now. And what should have taken me less than twenty minutes
is keeping me busy for eight hours now.

Does anyone have an idea what could cause this annoying behaviour?

Thanks in advance for any hints.

Alexander
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[NeddySeagoon]

fangorn,

A few things come to mind.

1. A bent pin on the CPU, so a signal is missing.
2. You didn't close the CPU socket lever ... it would be hard to fit the heatsink then.
3. Attempting to reuse the original thermal paste
4. Too much thermal paste.
5. you did not reconnect the 12v 4 pin or 6 pin header that supplies the CPU with power.

1. would mean a dead CPU. The pins normally break when you straighten them.
3 and 4 both result in the CPU going into thermal shutdown unless you have an older CPU that can't do that, in which case, it goes into thermal meltdown.
5. Oops but no harm done, there was just now power to the CPU.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[fangorn]

Thanks for the tips,

1. and 2. a Core i7 is BGA, so has no pins. And the socket is only closable in one position.
3. I had to remove the CPU to get that thermal paste off.
4. I used an old credit card to scratch as much off the heatsink as I could.
5. I reconnected all cables more than once. Including the two four pin connectors.

I planned, built and upgraded dozens of machines.

I just cannot believe that working hardware dies from powering down and up again. The only
part where I know this behaviour is on seasoned power supplies.

But again, thanks for the comments.
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[NeddySeagoon]

fangorn,

I guessed this wasn't your attempt at playing with the hardware but rule 1 is assume nothing.
As its a BGA CPU, ensure that the pads in the sockets are clean. Even a hair between the socket and a ball will make it not work.
The balls are fairly soft too. Ensure nothing is embedded in any of them. Inspect the socket and CPU with a magnifying glass for debris.

Do not use compressed air, a hoover or anything like that for cleaning. Fast moving dry air carries a high static charge, which can kill electronics.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[fangorn]

I agree that I have to disassemble the whole thing again.

Maybe I discover something this time.

I am off to screwing.

Thanks

Alexander
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[fangorn]

NeddySeagoon you were absolutely right.

To be precise, some of the tiny wire curls in the socket are bent and do not connect any more.

Now I can get myself a new mainboard.

Thanks again.
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[Chiitoo]

[NeddySeagoon]

Chiitoo,

I would use a natural bristle brush. Good quality paint brushes are ideal.
The bristles are conductive, so there is no danger of static build up.

This is enough to move the dirt from the fans and heatsinks to the bottom of the case, where its harmless.
If you want to move it out of the case, brush it onto a sheet of tinfoil.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[fangorn]

Chiitoo:
In BGA the connectors on the CPU are just small points of metal. The socket has to adjust for any
production variances. So there are small wire curls that can get pushed away if necessary.

This wire is so fine that any major movement will break it. Also if it is not setup correctly it can
connect to the wrong connectors and build a short circuit.

At the moment I am thinking if I should risk investing into an expensive socket 1366 board
and do not know if the Core i7 920 is damaged or if I go for new mainboard and CPU in
SandyBridge architecture for just 150 Euros more, which would allow me to abandon my
discrete graphics card. This is a number cruncher and needs graphics just to operate the
machine. The CPU power is not significantly higher with SandyBridge CPUs, but AFAIK the
power and thermal footprint is smaller. The longer I think about it, I tend to the "big solution".
I seems my local hardware dealer will make a fortune out of this.
_________________
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[NeddySeagoon]

fangorn,

Check online prices ...
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[Chiitoo]

NeddySeagoon,

I should have thought of that, of course...


fangorn,

I did take a look around a bit what it is about, thanks for the explanation also. ^^
I do prefer ye'olde spikes-into-the-hole scheme personally heh.

Best of luck in no other damage surfacing...
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Kindest of regardses.