Pc shuts down after three seconds without anything

[metansu]

Hello there,

Yesterday I thought it a good idea to replace the PSU of my four year old pc. Together with a new PSU I decided to replace the CPU fan and VGA fan (with Zalman fans). After installing everything I tried to boot the system, but at the exact moment I expect the system to 'beep' it powers itself down instead without any signal. The CPU and VGA and PSU fans all spin, the power LED on the mainboard is lit, as well as the on-board network LED, the DVD and HDD begin to start but then, after roughly three seconds it all ends. I tried removing everything and connecting the old PSU - but to no avail. Removing the memory will cause the mainboard to beep - and then shutdown. No signals on the screen as well. I tried removing the CPU (Athlon XP 2600+) with the result that the system won't shut itself off - but nothing else happens. I wonder what could have happend? Anyone got an idea? Thanks a lot in advance!

 

[haywood]

System specs please. List everything.

 

[PCD]

Sounds like either the CPU heatsink is not correctly seated or the CPU itself has got damaged. The heatsink on an AMD Athlon XP 2600+ can only be mounted correctly one way which is with the indent in the heatsink being placed over where it says Socket 462. If the heatsink is mounted the other way around it will not be seated correctly on the CPU and there's a high risk at crushing the edge of the kernel on the CPU.

 

[ForestCat]

Though it could certainly be other things, the most common "head slapper" with this is that the ATX 12V connector isn't plugged in. I missed this on a build once and saw the exact same scenario you describe.

If you haven't built a system lately, the motherboard has two power connectors now and both need to be plugged in. Everybody knows about the 20/24 pin power connector. The trick one is the ATX 12V connector which typically consists of a 4-pin connector that's in a box arrangement (some new motherboards & power supplies have an 8-pin EATX connector for this). If that one isn't plugged you will get the exact scenario you describe on boot up.

If that's not it, then my apologies and I hope someone else can find the solution.

 

[metansu]

I just finished checking everything, and the system is working again!
Yet I still don't know what the problem exactly was. I checked the power, and I am very sure that the problem wasn't power related. What I did find however that I porbably didn't apply the thermal patch correctly on the CPU. Not only did I find a piece of plactic covering on the thermal patch, but I also cut the patch in size, so it would fit exactly over the CPU core. After that the system didn't work however.

Only after cleaning the CPU again and applying thermal grease over the core and the tiny rectangular cicuits around the core AND fitting the fan over the CPU the system would start without shutting down. But still that was the only thing I got - the fans and hdd spun but nothing else happened.

It was then that I realized I had the CMOS clear jumper still in that position, and after swtiching back, the system would start fine !

So I guess I learned a couple of things from this:

1) Never apply a thermal patch without checking first
2) Always try to cover the area around the core
3) Just placing the fan over the (well prepared) CPU prevents a shutdown
4) Don't forget to switch the CMOS back to default
5) Never listen to some guy in a computer store who tells you taht your components are dead
6) Read the fora on TH instead

Anyway, thanks a lot everyone and if someobe has addidtional comments on this one, I would really like to hear about them. Maybe I did something right just by accident?

 

[PCD]

Though it could certainly be other things, the most common "head slapper" with this is that the ATX 12V connector isn't plugged in. I missed this on a build once and saw the exact same scenario you describe.

If you haven't built a system lately, the motherboard has two power connectors now and both need to be plugged in. Everybody knows about the 20/24 pin power connector. The trick one is the ATX 12V connector which typically consists of a 4-pin connector that's in a box arrangement (some new motherboards & power supplies have an 8-pin EATX connector for this). If that one isn't plugged you will get the exact scenario you describe on boot up.

If that's not it, then my apologies and I hope someone else can find the solution.

Ummm, for a AMD Athlon XP 2600+? They have never used the CPU auxiliary 4pin power connector.

 

[PCD]

So I guess I learned a couple of things from this:

1) Never apply a thermal patch without checking first
2) Always try to cover the area around the core
3) Just placing the fan over the (well prepared) CPU prevents a shutdown
4) Don't forget to switch the CMOS back to default
5) Never listen to some guy in a computer store who tells you taht your components are dead
6) Read the fora on TH instead

Anyway, thanks a lot everyone and if someobe has addidtional comments on this one, I would really like to hear about them. Maybe I did something right just by accident?

There is no need to cover the area around the core on an Athlon XP, in worst case you can short out the CPU if the thermal paste can lead a current. What did the trick was you removing the plastic that covered the thermal paste on the heatsink.