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Computer turns on and off. Dead cpu or mobo?

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February 24, 2012 2:13:57 AM

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-up...

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.
a b à CPUs
February 24, 2012 2:28:12 AM

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...
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February 24, 2012 2:32:24 AM

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)
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a b à CPUs
February 24, 2012 2:41:38 AM

"....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...
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February 24, 2012 2:47:40 AM

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
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February 24, 2012 4:03:55 AM

Okay I did what you said. Only cpu, psu, memory, and motherboard are connected. Same thing happens. Half the time it doesn't even start
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a c 186 à CPUs
February 24, 2012 4:29:52 AM

Most of the time when these things happen, it could be a bad power supply.
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a b à CPUs
February 24, 2012 4:30:42 AM

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...
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February 24, 2012 4:41:41 AM

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?
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February 24, 2012 4:43:07 AM

Also, when I take out the cpu, the whole thing wont run ever. And when I plug it in it turns on and off. Re-enforces my idea that it's the cpu
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a b à CPUs
February 24, 2012 4:45:17 AM

So you can no longer get video?

Have you checked your RAM? Maybe trying a single stick at a time.

CPUs VERY rarely go bad. And they usually don't slowly go bad, it's bang or bust.
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a c 186 à CPUs
February 24, 2012 4:56:34 AM

You touching the motherboard etc without grounding yourself could have caused a short to the psu.
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February 24, 2012 5:06:44 AM

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?
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a b à CPUs
February 24, 2012 5:22:36 AM

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.
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February 24, 2012 12:13:20 PM

I did het video for a while until it got too hot and probably died. How can I check the psu?
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February 24, 2012 12:40:07 PM

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?
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a b à CPUs
February 24, 2012 2:17:55 PM

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



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February 24, 2012 2:31:01 PM

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.
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February 24, 2012 2:38:09 PM

sonexpc said:
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


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.
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February 24, 2012 2:40:31 PM

kole9273 said:
I did het video for a while until it got too hot and probably died. How can I check the psu?


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.
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February 24, 2012 4:32:45 PM

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...
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!
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February 24, 2012 4:55:49 PM

you may have knocked out a transistor would be really bad LOL
what's your processor any?
sonex's suggestions would be mine as well ^^
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February 24, 2012 5:10:30 PM

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
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February 24, 2012 5:20:42 PM

wow! quite old dude! outdated too....
http://ark.intel.com/products/27520/Intel-Pentium-D-Pro...(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.

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February 24, 2012 5:28:49 PM

I don't want to spend money on a completely new processor And motherboard haha. I just want one that's slightly better than my last thats lga755. How would I know if I knocked a transistor? What would happen?
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February 24, 2012 5:52:46 PM

http://www.intel.com/support/motherboards/desktop/sb/CS...

that should be helpful. transistors are those capsule like thingy standing up in the motherboard. based on your video, they are covered with a black plastic sheet. old motherboard have longer transistors that you can budge if you're not too careful. Motherboards are littered with these things. Replacing them is complicated. You need expert level soldering skills and you need to replace them with the correct transistor too.

Well, basic physics about electronics and the "complete circuit". Knock one out then the circuit is open and the whole thing will not work.

About getting a new 775 motherboard. I think its better to find one that uses DDR3 ram modules since its faster and are now cheaper compared to DDR2 ram modules. DDR2 ram modules are getting extinct too which might give you problems soon (if ever your old RAM fails)
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February 24, 2012 6:04:25 PM

I may have actually bent a pin, but I'm not completely sure. I'll post a picture of it when I can.

Also, how can I tell whether a motherboard will work with all my current hardware? I want to upgrade it slightly, at the maximum ram allowed the motherboard (this one has a max of 4g).

Also, is ddr3 cheaper than ddr2 now?
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February 24, 2012 6:24:25 PM

yep. based on the 1st page on newegg's list of ram modules for sale today.

http://www.newegg.com/Store/SubCategory.aspx?SubCategor...

i think that should speak for itself :)  the cheapest DDR2 is $13 which is at 667 MHz, the cheapest DDR3 is at 1333 MHz which is faster (more than just twice as fast since speeds are exponentially larger as you go to higher speed)

like i said, you might be in trouble if you're still using DDR2 modules now... what more next year or even a couple of months from now. DDR2 is an old technology which is practically obsolete now if you ask me.
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February 24, 2012 11:02:02 PM

Will that motherboard work well or not? Someone please help
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February 25, 2012 2:07:08 AM

kole9273 said:
http://www.newegg.ca/Product/Product.aspx?Item=N82E1681...
What about this motherboard? Will everything work with it, including my graphics cards? (Obviously the memory wont)


Yes, this is a nice board. It's actually too nice for the price. It's a decent entry board with an 7.1 audio channel output.
Based on this:
http://www.msi.com/product/mb/G41M-P28.html#/?div=CPUSu...
it supports your Intel Pentium D 945

I saw the video, yeah there's an odd looking bent in the socket. That might be causing it. If possible, get help to test if it affected the CPU. Test it in a working 775 socket unit.
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February 25, 2012 6:55:25 AM

Yeah, that does look like a broken off pin in the video of the socket. Might pay to have a really close look at the socket with a magnifying glass , so as to compare what is sticking out the socket with the actual cpu pins.

If it certainly is a pin, then perhaps what happened is that it was crumpled when you origianlly took it out/put it back , thus perhaps it either fouling another pin or not making proper contact into its own pin socket, or both of course. Also of course, it makes your joice of action pretty clear.

As you are already accepting that a full cpu/board upgrade is needed, then thats what you need to be doing. I would build an idea of what you want/need then I would go to a pro, get them to do it for you. Will cost you more...but...

You wiill already be a bit sore at what you have done, probaly kicked yourself blue already, don't allow yourself to do it again, you'll be looking for a tall building to jump off :lol: 

If you do want to learn about the techie/build side of PC's, then spend some while reading Motherboard manuals, you can download plenty from makers websites , other components as well.

Then perhaps buy a cheap machine off ebay/whatever to play around with, or even buy a load of old bits , see if you can get a working machine from it. Thats how I became self taught, back in the early 90's, it was a lot harder then as well, comprehensive manuals of help to a self builder being rare birds, luckily I knew the owner of an electronic repair business , so was able to pick up badly sectored RLL hard drives, that kind of thing. It does not matter too much if you mess something up that cost little or nothing.
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February 25, 2012 9:33:53 AM

True indeed. Computers are not really complicated once you study them. It's actually fun to study them and it's kinda addictive too. Upgrading and going with what's new can be very addictive... trust me... anyhow, it's important to know the basics and actually get to build and maintain your own unit without the help of professionals. :) 
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