# Little help - dead Mobo or CPU...?



## Culhwch (Mar 10, 2011)

So, computer problems. I'm hoping some of the brilliant minds here can give me a little guidance...

A couple of nights ago my wife's PC went to sleep, and it wouldn't wake up. No response at all - keyboard, mouse, power switch, reset switch, nothing. I ended up getting it to switch off by cutting the mains power. When I tried to switch it on again, the PC powered up, but nothing happens - it wouldn't even post. The only improvement was that the power switch does now switch the thing off. 

Tonight I pulled everything - video card, hard drives, optical drives, RAM - one by one to see if it made a difference. No dice. Stripped it right back to the motherboard and processor, and it's still dead. I figure it's one or the other that's died. The only thing I haven't tried is the PSU - I'll swap that out this weekend, but I don't figure that's the problem.

So what I'm left with is trying to figure out which it is, the motherboard or the CPU. Anyone have any advice on which it might be, or how I could easily determine the problem? I could swap out out the processor into my machine, but I'm not too keen to do that. It might just be easier to buy a couple replacements. But I'm open to thoughts. I'm a rank amateur at this stuff, really...


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## cornelius (Mar 10, 2011)

Maybe there's a problem with the current, but I wouldn't start to tinker with that. It's weird that it doesn't do anything at all. A friend of mine had MOBO problems once, but the "light" of the start up button still worked. I wouldn't know about the CPU though. At most, I'd try to switch the cable, see if the box is just without juice or something. No lights usually mean no power.

Don't put stuff from a broken computer into a working one unless you're absolutely sure the damage it might cause won't go beyond repair.


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## Culhwch (Mar 10, 2011)

No, there is definitely power. The lights come on, the fans come on, but nothing else happens. The lights are on, but no one is home. The only power problem I can think of is if there's not enough juice, but as I said I think that's a long shot...


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## cornelius (Mar 10, 2011)

Sounds like Mobo acting like a HoBo (Horror Board), what's the type of said computer? Age? MoBo brand? I have a couple of MoBo's on the "black list", if it's on said list, the chances of a MoBo melt down is possible. Did it get hot? Is there a lot of dust in the fan? If the computer wouldn't get enough power, it's more likely to "blink" then just to turn on the lights. 

I'm not a specialist, so my guess is as good as anyone's.


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## The Ace (Mar 10, 2011)

Check your MoBo's capacitors, if one's blown it can take down the whole thing.


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## Culhwch (Mar 10, 2011)

I've had a good look over the motherboard and can't see anything amiss. It's a Gigabyte board, don't have the model number handy. It's probably three or so years old. I'd call that fairly young, but these days I guess not so much....


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## chrispenycate (Mar 10, 2011)

Culhwch said:


> No, there is definitely power. The lights come on, the fans come on, but nothing else happens. The lights are on, but no one is home. The only power problem I can think of is if there's not enough juice, but as I said I think that's a long shot...



I recently had a similar situation; no Bios, no signs of life beside the fans coming on, and a solitary click from the DVD burner.

Finally, after having changed the mother board it turned out to have been a power supply fault, despite the voltages on all legs being correct, even under load. (how odd's that then?)

New PS, nicely overrated, and everything worked as before.


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## Vertigo (Mar 10, 2011)

Yes I would check the PSU. It has more than one output so it might be supplying power to some parts of the computer (hence lights, fans, whatever) but not to other parts.

Unless your two computers are absolutely identical do not try to swop CPUs They will almost certainly need different chipsets unless they are absolutely identical models. And to be honest I would not advise pulling the CPU unless you have the right kit for handling, extracting and inserting it. I know many of the newer ones are a lot easier to handle than they used to be but they are still incredibly sensitive to static and such like.


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## cornelius (Mar 10, 2011)

It's a shame we can't meet up and have a little go at it, with all our forces and tools combined, imagine what we could do 

It does sound like a MoBo error. We had it too with the "main computer", sound exactly like what's happening to you.


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## Culhwch (Mar 10, 2011)

chrispenycate said:


> Finally, after having changed the mother board it turned out to have been a power supply fault, despite the voltages on all legs being correct, even under load. (how odd's that then?)
> 
> New PS, nicely overrated, and everything worked as before.


 


Vertigo said:


> Yes I would check the PSU. It has more than one output so it might be supplying power to some parts of the computer (hence lights, fans, whatever) but not to other parts.


 
Well, I hope that's the case here, it'll be much easier to fix. I'll try my (functioning) PSU tomorrow and see if that works...



> Unless your two computers are absolutely identical do not try to swop CPUs They will almost certainly need different chipsets unless they are absolutely identical models. And to be honest I would not advise pulling the CPU unless you have the right kit for handling, extracting and inserting it. I know many of the newer ones are a lot easier to handle than they used to be but they are still incredibly sensitive to static and such like.


 
They're not identical, but they are closely related. Same family of motherboard and processor. But I really don't want to do this, so I probably wouldn't even as a last resort.



cornelius said:


> It's a shame we can't meet up and have a little go at it, with all our forces and tools combined, imagine what we could do


 
If you pay your own way I'm happy to cook a nice meal for you all!


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## Deathpool (Mar 11, 2011)

Culhwch said:


> So, computer problems. I'm hoping some of the brilliant minds here can give me a little guidance...
> 
> A couple of nights ago my wife's PC went to sleep, and it wouldn't wake up. No response at all - keyboard, mouse, power switch, reset switch, nothing. I ended up getting it to switch off by cutting the mains power. When I tried to switch it on again, the PC powered up, but nothing happens - it wouldn't even post. The only improvement was that the power switch does now switch the thing off.
> 
> ...


 
This is just something that I've read in my A+ certification book. If the computer turns on and nothing appears on the screen it can be four things. That is the graphics card, ram, motherboard, or processor. According to the book the best way to figure it out is if there's a spare part that you know is good try it with all parts installed. If doesn't work try until it does. That's just what I read in my book. I'm not sure, but the power supply's output might have to be compatible with the processor's power consumption.


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## Vertigo (Mar 11, 2011)

Generally best to get an overrated PSU - ie. more power than currently required. Big danger  with PSU's is they are designed to work with your initial computer set up and then you add loads of extra drives, cards etc. and suddenly you are pushing the limit. I would take the old one down your local computer shop and ask for one with somewhat more oomph (you know that word should really be in the dictionary) than the original. For the difference in cost it is well worth doing.


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## Deathpool (Mar 11, 2011)

I believe the way to do that would be to check the voltage required by the processor against the voltage the power supply converts 110 to. It's 110 if you live in the United States. The same thing that I said about the processor being compatible with the power of the given out by the power supply applies to graphics card. I haven't hurd about the ram. If the power supply is more than the processor can handle it could burn it out.


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## chrispenycate (Mar 11, 2011)

Trouble is the 550 watt model I installed actually had lower peak current ratings on a couple of the supplies (notably the ±12 volts) than the 500 watt one it replaced. Though, for the BIOS, it's the +3.2 volt supply which counts. 

It has outputs for several more hard disks; as regards total power it should have been wildly within limits. And its dual speed fan has, as far as I  can tell, never gone into "hot" mode.

Add to this the fact that all the voltages looked good on the DVM, with the thing plugged in and fans turning, little red light behind the touch screen the fact that a new power supply cleared the problem is a straight insult.

And "oomph" in my dictionary is:- _(slang)_ vitality, enthusiasm, sex appeal or personal magnetism. I suppose it is the last of these a switch-mode power supply requires in quantity.


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## Vertigo (Mar 11, 2011)

I confess I didn't check Chris and just assumed it wouldn't be there  but yes I think that last definition would probably be the one.

DP - what I was referring to was the max *watts *the psu is rated for. You certainly would not want to put out more *volts* than the components expect otherwise things would get very expensive. However having a PSU that is rated at only just or even less watts than is being drawn will result in a very hot PSU and probably get expensive again!

In fairness Chris, as I'm sure you're aware in your line of work, a failed PSU doesn't necessarily mean it has been overloaded. It may just be old and tired (like me) or just some silly component that has decided to give up the ghost.


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## chrispenycate (Mar 11, 2011)

It is not power supplies I am grumbling about, but switch-mode power supplies. Somebody just brought me round a little fifteen year old console and I found and replaced the deadode (a diode which has) in minutes; longest was finding which screws gave access. SMPS are the work of the devil, and the people who decide to put double sided sticky tape so it can only be prized out direct employees. When power supplies blow up they are supposed to stop giving volts and give smoke, or at least total lack of anything.

Oh, all right, rant over. They're cheap and lightweight; I just can't mend them.


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## Deathpool (Mar 11, 2011)

Vertigo said:


> I confess I didn't check Chris and just assumed it wouldn't be there  but yes I think that last definition would probably be the one.
> 
> DP - what I was referring to was the max *watts *the psu is rated for. You certainly would not want to put out more *volts* than the components expect otherwise things would get very expensive. However having a PSU that is rated at only just or even less watts than is being drawn will result in a very hot PSU and probably get expensive again!
> 
> In fairness Chris, as I'm sure you're aware in your line of work, a failed PSU doesn't necessarily mean it has been overloaded. It may just be old and tired (like me) or just some silly component that has decided to give up the ghost.


 
This usally happens to me. I end up saying something just to be proven wrong later on.


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