Computer turns on and off. Dead cpu or mobo?

kole9273

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Hello Everyone!

My computer has stopped working, it keeps shutting off and on. I have narrowed it down to what I think is a dead cpu or mobo. I'll explain how this happened:

I'm a completely newbie/ not very educated in computer hardware. I opened up my computer just to take a look at it and mess with some things. I took off the cpu fan and the cpu, and then I replaced it back in (without putting more thermal grease, which I did not know about at the time). I put everything back together and started up my computer. It didnt want to start at first, but then it started normally. I updated my Bios, and while it was updating my computer shut off mid-update. I turned it back on and it said that the cpu had overheated, and then it started normally again before it finally shut off and never returned to the POST screen.

Nothing shows up on the monitor. It may just stay running or shut on an off. After i put it back together it had beeped the code for a thermal trip (indicating cpu overheat or not enough thermal material).

I'm not very good at explaining things, so I made a short video showing my messed up computer in action: http://www.youtube.com/watch?v=iMGhELkrTok&feature=g-upl&context=G22fe990AUAAAAAAAAAA

Please help me figure out what is wrong.
Thank you everyone in advance! I know I was dumb messing with my computer without much knowledge in the subject, lesson learned.
 

sonexpc

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While you put back the cooling fan on the cpu ... did you take out the whole Motherboard and exam the mount.......I thing is bad contact cause your CPU overheart... take out the whole motherboard and remount the CPU Fan... make sure all 4 leg go thur the other side of the board...
 

kole9273

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I never tookout the motherboard. I'm pretty sure all 4 legs are through the other side of the board, the fan doesnt wobble. I put grease in between the two and the motherboard no longer makes a cpu thermal trip beep anymore. and I can tell the heatsink and the cpu are touching because I took it off again, and you can see that the thermal grease is touching both the cpu and the heatsink.

Also, all of the fans run. I doubt it's the PSU. Could something be shortcircuiting? Or is it really just the motherboard or cpu? ( those are the only two things I messed with)
 

sonexpc

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"....and you can see that the thermal grease is touching both ...."

I didn't see this on the video.....

But anyway this is what I suggest ... Take out the motherboard ... only put the cpu and memory on top and just boot from the Power Supply with out any other device connect ... this is what I suggest .... you do or not is up to you...

The intel Original Fan design is really bad... lot of people think it is mount ok.... but finally is not.... and don't put too many grease in between.... .... and while you apply need grease do you clean up the old one...
 

kole9273

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I meant that before this video was made, I had taken out the fan again and applied grease like I should have done in the first place. So now it no longer beeps.

Yeah I'll try that
 

sonexpc

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That means these four items..... at least one have problem...If you got lucky to start can you gp to BIOS ASAP to see what temp it is or what is the Voltage Reading from the power supply ... and once again take a look at the back of the motherboard make sure all 4 black LEG is go thur...... do you have other system to swap parts to test or this is the only one...
 

kole9273

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I'm pretty sure the psu and memory are fine because the only thing I messed with was the cpu. I don't understand how the power supply would go bad from that. This is the only one. I'm thinking it's the cpu. Should I try replacing it?
 

kole9273

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No I cannot get any video. I have tried 2 different sticks of ram. Well yeah usually they don't, but this one didn't have the heatsink/fan attached to it because there was no thermal grease, so it overheated Very quickly. Yeah it could be the psu.. but then why did it successfully start up at first before shutting down mid-bios update because of cpu overheat?(I had successfully gotten into windows and downloaded the bios update) After that it stopped working. So the psu had to be powering the system fine then right?
can a interupted bios update cause something like this to happen?
 

Raidur

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Your CPU could have very well been overheating due to you not reapplying thermal compound.

However it is possible there is and underlying issue (like the PSU).

However you should at least get video however your CPU is seated/pasted as it will take a little bit for it to heat up.
 

mahatmacoat

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Have you taken out the cpu again and checked it? Is it a pin type? If so, have you bent a pin?

If not, is it seated correctly?

Simple fact is, you only messed with the cpu and fan , so *unless* you hit the mobo with
static through not being grounded , its 99% that your problem is one of those 2 things.

Did you disconnect and take out the H/Sink fan? If so , did you reconnect it to the correct pins,
or inded, the correct way round on the pins?
 

sonexpc

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Try to find speaker to connect to the MB ... there should ba a cable inside the case to do that....

Remove all memory and start the system :

1, if no Beep that high chance is motherboard
2, will the Keyboard Connected.... while you switch on the computer see any light on the num lock flash.... if not flash high chance is motherboard.

"...... I updated my Bios, and while it was updating my computer shut off mid-update...."..... this may be the major issue but I don't understand why it will start up one time after that...... DO you know how to rest the BIOS.. ( it may be easy for you to choose remove the battery on the MB and put it back)

And because of this .... I will think is MB instead of CPU



 

najirion

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its still very unlikely that the CPU would die due to simple overheating. It has a fail-safe wherein your system will shutdown automatically when overheating. CPUs are generally tougher than motherboards. I bet its the board. If you removed the CPU from the socket, make sure the socket is totally clean (free from any hair or dust). Check the 4-pin and 24-pin power cables if they are plugged well (if you did unplug them somewhere in your hardware adventure). If the bios update totally failed just reset it.. Remove the CMOS battery for a while (like 1 minute), put it back on and try starting your unit.
 

Goldengoose

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If still doesn't work after this - i would suggest seeing if you have any other parts you can sub into the machine and diagnose the problem part.
 

najirion

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The unit was fine even before you dismantle them right? The PSU is fine I bet on it. Faulty assembly doesn't usually get the PSU broken... faulty assembly will likely cause the PSU to destroy other hardware (like the motherboard). If it the PSU was working fine even before your disassembly, im sure it is still fine now. It's also dangerous to troubleshoot the PSU unless you enjoy electrocution that is.
 

kole9273

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It doesn't look like a bent a pin.. *can anyone get me a high-res picture of the socket? (Lga775 socket) Yes I put the fan back in correctly. The cpu is also placed correctly. I tried to stay grounded, but I still may have messed up the mobo.

I can't test the system right now by taking out the memory, but I will when I get back home.
I have tried both taking out the battery and doing the jumper to try and reset the bios, still didn't work.

Yeah the system worked perfectly before I dismantled it. I'm 99% positive its the processor or motherboard.

P.S. this is my motherboard: http://ark.intel.com/products/23503/Intel-Desktop-Board-D946GZIS
If I need to replace this, can anyone suggest me a motherboard to upgrade to? Preferably one that uses the lga775 socket. And one that all my current hardware can run on? And that has 2 pcie slots? Its fine if it uses ddr3.

Thank you for all your guys help!
 

sonexpc

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kole9273

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I just ordered this Intel Pentium D 945 3.4GHz 4M/800MHz x2 Dual Core LGA755 SL9QQ 3734B019 because I wanted to upgrade my cpu anyway. That's why I have to have a lga755 motherboard. Hopefully one that supports more than 4gig ram also
 

najirion

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wow! quite old dude! outdated too....
http://ark.intel.com/products/27520/Intel-Pentium-D-Processor-945-(4M-Cache-3_40-GHz-800-MHz-FSB)

that right?
its a 95watt processor. quite power hungry considering that G620 (the one sonex is suggesting) is only 65watt processor and far more faster too... RAM capacity supports today is basically based on the operating system (for windows, i dunno about mac). 32bit can only support 3.5GB of ram while 64bit is capable of almost anything (i forgot the limit but its way too huge for motherboards)
g620 has an integrated graphics too.