My PC will not power up at all, after thinking it was the PSU I replaced that to no resolve. When I try to power on the PC the CPU fan will move about 1mm and then nothing.

I tried all sorts, but it seems removing the 4 pin power cable for the CPU will cause the motherboard to function (spins the CPU fan, PSU fan and SYS Fan as well as lights up the power light).

This lead me to believe that the issue may be that the CPU is broken or the socket is broken on the motherboard, I did attempt to bake the motherboard for a few minutes to reset the solder but nothing happened it remains the same (motherboard will only work with the CPU power cable unplugged.)

I don't have a spare cpu to try so I'm hesitant to whether I should buy a replacement motherboard or cpu first... any insight would be greatly appreciated.

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    What's the PC? are there any error messages/beeps? Is this a new build or an old one? Have you changed anything recently? – Journeyman Geek Aug 12 '13 at 1:12
  • Before you "baked" the motherboard, did you inspect the area of the voltage regulations stuff surrounding the cpu itself? Did you inspect the socket top and bottom with the cpu removed from the socket? When you replaced the PSU and plugged a 12V wire (4pin) into the motherboard, did you check that the wiring is correct (color coding and manuel)? – Psycogeek Aug 12 '13 at 2:11
  • I also note bent pins on LGA motherboards often manifest themselves as motherboard 'errors'. Once again, not enough information to tell. We need more juicy details! – Journeyman Geek Aug 12 '13 at 3:15
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    This is an existing PC, nothing has changed it just died randomly. There are no errors because the PC will not even boot. I am using the correct cables (consulted the motherboard manual as well). I could not identify any bent pins or any issues with the socket, but it's hard to tell because it's a FM1 socket and covered in plastic :( – HelloSpeakman Aug 13 '13 at 7:29
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    I should probably specify that before the PC died, I tried to play Dead Island on Steam, it caused my PC to restart after a few minutes. It was logged as a "Kernal-Power" error in the event log. I tried to get this to run around 6 times before giving up. I fell asleep with the PC still on and when I awoke it was dead. I kind of think maybe the "Kernal Power" issue pushed something to break... – HelloSpeakman Aug 13 '13 at 7:41

You haven't specified if this is a new build, or if this is your existing system, but here are a few non obvious things to check:

Before I offer some suggestions, here is why putting your motherboard in an oven is a REALLY BAD IDEA

Capacitors are full of electrolytes which react to heat just like water. Putting a capacitor into an oven could figuratively boil off all the liquid inside. You do not want to heat up capacitors.

Ever heard of xbox's getting the red ring of death, and that you can fix it with the 'towel trick'? Bad idea.


4 Pin Connector Since removing the 4 pin connector causes it to work (as far as you have stated), then this is likely a power problem. Two very important things to consider.

Accidentally using the power supply 4 pin
Many 24 pin power connectors are also 20 pin connectors. Those 4 extra pins will fit into the cpu 4 pin header, but they have the wrong pinout. While this is a very slim chance it is the answer, I have seen this before from new system builders.

enter image description here

Accidentally using a GPU 4 pin connector
I've also seen 6 pin and 8 pin gpu headers plugged into the cpu 4 pin headers.

Bent CPU pin
A bent pin on the cpu can also cause the problems you are describing.

Bad Capacitors

If this isn't a new build, check to see if you have any blown capacitors.


Modular Power Supplies

If you replaced your power supply and it happens to be modular, make sure you use the cables that come with the PSU. There is no standardization between manufactures for modular pinouts. You can kill your components if you don't.

See this super user question How do I interpret the Asus motherboard LED and beep patterns?

Is the CPU bad?

I've repaired computers for 15 years. I've only ever seen 2 cpu's 'go bad'. It is almost always the power supply then the motherboard. I suggest that you buy a new motherboard.

  • Baking is only useful as a 'cheap' way to fix BGA elements that have come off, very specifically for 8xxx series nvidia graphics cards, and units with their mobile version. These are usually off warranty, old, and prepared very carefully to shield everything but the processor... and even then you're better off with a hot air gun or proper reballing. – Journeyman Geek Aug 12 '13 at 3:32
  • @JourneymanGeek - Aye. If we are not talking about a soldering problem baking very often does more damage then it solves. – Ramhound Aug 12 '13 at 11:48
  • Yes I was using the correct CPU cable, my 24 pin was separated but I plugged them in together as they sort of attach. I couldn't identify any bent pins - I suppose it could be the capacitor I can research that a bit more. Also I baked the motherboard at a somewhat moderate temperature for a short period of time, I was skeptical but advised I had nothing to lose as I will need to replace the motherboard anyway - I wouldn't have tried otherwise. The downside is that my GPU is onboard (can be removed) so I may need to buy a new GPU also, unless the new mboard supports it. – HelloSpeakman Aug 13 '13 at 7:34

The most likely failure is the power supply. Try replacing that first.

BTW, if you are doing a heavy rebuild, replacing the power supply is a usual, so nothing is lost there.

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