# Mobo won't power on - 8 pin CPU atx 12v?



## LifeOnMars (Jan 31, 2010)

Now here's what I've found: I can connect the 24 pin ATX power cable and the entire computer will turn on: the fans and everything else is running, all except for the CPU which isn't receiving power and the graphics card doesn't spin up. As soon as I plug the 8 pin ATX 12v cable that's supposed to power the CPU, the computer will no longer turn on. It'll turn on for a milisecond and instantly turn itself off.

I am using -

antec 900
fsp everest 800w psu
p5n-t deluxe mb
q6600 go
true 120 cooler
4 gb xms 2 corsair 800
320 gb seagate sata ii HD
bfg gtx 275 oc

so what could be the problem guys? Grounding issue?psu? Dead mobo or CPU?

What's the minimum you need for it to power up, for example would it power on without the graphics card in place?

It someones old system that I have bought so I know all the components have worked together.


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## LifeOnMars (Jan 31, 2010)

Anyone help in anyway on this please?


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## theonedub (Jan 31, 2010)

You will need a GPU since there is not an onboard solution. Try using the 4pin 12v AUX plug instead of the 8pin and see if it does the same thing. Are you sure the GPU is installed correctly and plugged in as well? As always try it with CPU, GPU, 1 stick of ram, no HD, and see if you can get it to enter the BIOS.


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## Mussels (Jan 31, 2010)

mobo, PSU, ram, video card. Thats the minimum for a power on.

the fact that its turning on then off again, means its detecting something is wrong - likely, you forgot something.


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## LifeOnMars (Jan 31, 2010)

Hi and thanks for the reply. It comes with two 4 pin plugs and I have tried it with both, and each one on their own all with the same result. Without any CPU power plugged in the psu fan spins, the case fans spin, the fan mounted to the true spins, the DVD has power, but the graphics card does not spin. When CPU power is added it turns on then instantly off


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## LifeOnMars (Jan 31, 2010)

Mussels said:


> mobo, PSU, ram, video card. Thats the minimum for a power on.
> 
> the fact that its turning on then off again, means its detecting something is wrong - likely, you forgot something.



Hi mussels. I have 24 pin, 8 pin atx, two pcie 6 pins, case power switch connection, ram in place, case fans, CPU fan all connected... Anything I have missed?


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## Mussels (Jan 31, 2010)

that list just confuses me 


Motherboard: 24 pin, 8 pin, any aux power it needs (floppy/molex connectors, some boards have em)
Video card: all PCI-E power connected
Ram: one stick, try various slots. if no luck, try another stick in several slots.

During this, everything else should be disconnected. no HDD's, no DVD burner, no fans except for PSU, CPU and VGA.


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## LifeOnMars (Jan 31, 2010)

Sorry for any confusion  as the true is passive it's ok to try turning on the system without it's mounted fan isn't it?


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## theonedub (Jan 31, 2010)

Unless that board has a feature where it does not power on if there is no fan connected to the CPU Fan header. Might want to check that out.


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## Mussels (Jan 31, 2010)

theonedub said:


> Unless that board has a feature where it does not power on if there is no fan connected to the CPU Fan header. Might want to check that out.



^ what he said.

make sure the fan you use has an RPM sensor as well, or it wont detect it. (hint: use the fan from the stock cooler)


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## LifeOnMars (Jan 31, 2010)

Also if I have no joy with the above suggestions is it worth setting the whole thing up outside the case to make sure the case is not shorting it out?


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## Mussels (Jan 31, 2010)

LifeOnMars said:


> Also if I have no joy with the above suggestions is it worth setting the whole thing up outside the case to make sure the case is not shorting it out?



yes.


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## LifeOnMars (Jan 31, 2010)

Ok just tried it all outside of the case and tried it with 4 different sticks of ram in all 4 slots individually. Exactly the same outcome  but hopefully at least, that rules out any shorts happening inside the case. I also cleared the CMOS a few times just to check that as well. I have another psu arriving Monday so hopefully that may solve the problem or at least narrow the cause of the problem down a bit.


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## Mussels (Jan 31, 2010)

the only real thing left for you to do, is swap components with known good ones - test CPU, ram, PSU, and video card in another machine for example.


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## LifeOnMars (Jan 31, 2010)

Mussels said:


> the only real thing left for you to do, is swap components with known good ones - test CPU, ram, PSU, and video card in another machine for example.



Yeah and that's where things really suck. I've had to wait ages to afford to get this and then this well hopefully I can eliminate the power supply tomorrow and then take it from there...I'm absolutely gutted but that's life I guess. Thanks for the help so far guys and I'll keep updating the thread with any success or findings.


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## dr emulator (madmax) (Jan 31, 2010)

you haven't got the 8 pin mobo plug mixed up with your pciexpress plug? that would spell smokin mobo 
have you tested the psu with a multimeter in situ?


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## LifeOnMars (Jan 31, 2010)

dr emulator (madmax) said:


> View attachment 32693 you haven't got the 8 pin mobo plug mixed up with your pciexpress plug? that would spell smokin mobo
> have you tested the psu with a multimeter in situ?



Nope no mix up on the plugs. Don't have a multimeter and can't really buy anything else at the moment so I'm stuck. Another member from the uk has said he will help by testing components on his system so will try new power supply tomorrow and if there is no joy I'll start posting him stuff to test out for me...that's if I can afford postage,yes, it's that bad.


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## dr emulator (madmax) (Jan 31, 2010)

shame ya don't live near me


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## LifeOnMars (Jan 31, 2010)

I moved here recently and don't really know anyone locally although I think alexp one of the moderators lives around my neck of the woods.


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## LifeOnMars (Jan 31, 2010)

I'm bored so I'm gonna remove the thermalright ultra and clean it. The idiot who shipped the computer left it attached so whilst I have it removed I'm going to check the CPU and socket for any damage. As I have only used amd previously is there anything that would signify damage to the processoer or the socket? also what's the best thing to use for cleaning the thermalright ultra, I was just going to use a cotton bud to clean all the dust of it, is that ok?


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## brandonwh64 (Jan 31, 2010)

look for bent pins in the CPU socket and if there is then thats your culprit


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## Bo$$ (Jan 31, 2010)

plug in the cpu 8pin,take out the graphics card, does it still turn off?


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## LifeOnMars (Jan 31, 2010)

Cheers brandon for your continued support mate


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## brandonwh64 (Jan 31, 2010)

YW. this problem seems like as i said in the other thread that it could be a bad motherboard or a corrupted bios but its hard to tell. if you can find another motherboard or CPU to test that would be best


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## dr emulator (madmax) (Jan 31, 2010)

ye it's a shame you don't live near here, as i would have been able to whisk that cooler of to my uncles garage, and use the air compressor to blast the dust out , if it's aluminium i would wash it under the tap then use a hair dryer to dry it out


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## LifeOnMars (Jan 31, 2010)

Bo$$ said:


> plug in the cpu 8pin,take out the graphics card, does it still turn off?



Cheers , I'll try that after I have cleaned the heatsink and reseated the CPU


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## Bo$$ (Jan 31, 2010)

dr emulator (madmax) said:


> ye it's a shame you don't live near here, as i would have been able to whisk that cooler of to my uncles garage, and use the air compressor to blast the dust out , if it's aluminium i would wash it under the tap then use a hair dryer to dry it out



umm, it wouldn't turn off that quick, i had the exact same issue, turned out to be my 8800gt was faulty


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## dr emulator (madmax) (Jan 31, 2010)

no i was talking about cleaning the cooler probably is his card 
like i've always said it's hard to diagnose someones problems unless it's in front of you (and even then pc's can be a pain  )


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## LifeOnMars (Jan 31, 2010)

Ok so cleaned the cooler checked the CPU which looked immaculate underneath. Examined the CPU socket very closely and no bent pins or alien objects in there then reseated the CPU and remounted the true which is getting alot easier to do the more I do it hooked up the psu and whilst connecting the 24pin plug I noticed a hollow one without a pin in it...is that normal ? Anyway connected the other things and exactly the same.


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## LifeOnMars (Jan 31, 2010)

Also noticed a cable coming from the top of the case inside which has like a metal ring at the end, anyone know what that is ?


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## 95Viper (Jan 31, 2010)

LifeOnMars said:


> whilst connecting the 24pin plug I noticed a hollow one without a pin in it...is that normal ?



Yes, I believe pin 20 is not used.

See, here and here.


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## Bo$$ (Jan 31, 2010)

LifeOnMars said:


> Ok so cleaned the cooler checked the CPU which looked immaculate underneath. Examined the CPU socket very closely and no bent pins or alien objects in there then reseated the CPU and remounted the true which is getting alot easier to do the more I do it hooked up the psu and whilst connecting the 24pin plug I noticed a hollow one without a pin in it...is that normal ? Anyway connected the other things and exactly the same.



are you even thermal paste?  because that in itself will cause this type of issue


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## LifeOnMars (Jan 31, 2010)

Bo$$ said:


> are you even thermal paste?  because that in itself will cause this type of issue



Sorry,yes there is thermal paste applied.


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## Bo$$ (Jan 31, 2010)

LifeOnMars said:


> Sorry,yes there is thermal paste applied.



oh, good 

 did you test it without the graphics card?


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## 95Viper (Jan 31, 2010)

Can you post a pic of the cpu power connector and one of it plugged in the MB?  I am curious.


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## LifeOnMars (Jan 31, 2010)

Bo$$ said:


> oh, good
> 
> did you test it without the graphics card?



Yep, I tested it with and without both with the same results. When I put it in I actually must have not pushed it in fully as when I powered on a red light appeared next to it's pcie slot, once I reseated it this disappeared.

Also any clues on what the cable is coming from inside the case at the top with a metal ring connector on the end is for?


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## LifeOnMars (Jan 31, 2010)

95Viper said:


> Can you post a pic of the cpu power connector and one of it plugged in the MB?  I am curious.



Unfortunately not as I'm posting from an iPod touch, my only access to the net at the minute. What are you curious about... Share with me


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## 95Viper (Jan 31, 2010)

I wanted to see if the wiring on the connectors was screwed up.  It should be, I believe, yellow w/ blue stripe wires on the clip side and black on the smooth side. Whether it be two 4 pin or one 8 pin.

They should be labeled P2.

Like I said, just curious.


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## LifeOnMars (Jan 31, 2010)

It's a good point and I'm open to checking anything as I'm desparate to have a working rig so thanks for that mate, they both seem perfectly wired. Oh well I'm just gonna keep pressing and guessing


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## LifeOnMars (Jan 31, 2010)

Other than pleading with it to power on and boot up I've run out of ideas for today. The most expensive paper weight I have ever bought new power supply tomorrow that I can try.


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## Bo$$ (Feb 1, 2010)

have you tried different ram? or at least 1 stick at a time to see if you dont a have a bad one


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## LifeOnMars (Feb 5, 2010)

Ok for those who have offered advice or are just generally interested here's an update. I managed to find a guy locally who tested all of the components in his rig and it turns out it is the motherboard!! So bad news really but also good in the sense I can now go about solving the problem. Can get a new motherboard on Wednesday and rma for this one.

So, the next question is which mobo?

I need it to have good overclocking capabilities,
needs to accept the corsair xms ddr2 800 memory, have enough room for the thermalright ultra 120 and accept a q6600 without any bios malarkey

suggestions would be very much appreciated - budget would be about £70-90 tops, preferably as low as possible


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## brandonwh64 (Feb 5, 2010)

a gigabyte P45 is a good board


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## Bo$$ (Feb 5, 2010)

i think he means this: http://www.ebuyer.com/product/155486 or this? http://www.ebuyer.com/product/170162


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## brandonwh64 (Feb 5, 2010)

this is my choice "Asus P5QD Turbo iP45 Socket 775 8 channel audio ATX Motherboard"


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