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Solved PC won't turn on

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JohnCarter290822

JohnCarter290822

PCHF Member
Aug 20, 2020
2
0
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#1
Hello,

Motherboard: p8z77-V
CPU: intel i5 3570k
RAM: 2x 8GB HyperX Fury
PSU: Corsair CX650
GPU: GTX 650 Ti

I was using my pc as usual when it sundelly turned off. I tried to turn it on again, but the cooler worked for half a second, and then the PC turned off. The power light from the motherboard keep lit during the whole time sinalizing that it was being feeded...
Then i tested the PSU separateddly, it worked just fine. I've also tried to test the GPU, CPU , and RAM in another PC with the same configurations and it also worked normally.
Something weird that was going on was that when i took off the 8pin from the CPU the cooler turned on for half a sec and then turned off, then when i put it back again nothing happened...
 
#2
Hello JohnCarter290822,

JohnCarter290822 said:
I've also tried to test the GPU, CPU , and RAM in another PC with the same configurations and it also worked normally.
Click to expand...
Try the PSU from the other computer in your computer and first of all by not by having the add on GPU in the board and only using the integrated video.

As a PSU puts out various voltages +3.3V, +5V and +12V it may appear that the PSU is working correctly but it is not, any significant drop of any output can prevent the system from booting up, the other scenario is a significant increase in the output which can be worse as it can fry one or more major components such as the MB, CPU, RAM, add on video card etc.
 
#3
I put the PSU of the other computer (also a CX650) on my motherboard and it gave the same problem.
I tried to use my PSU on this another PC and it worked normally.

At the moment, I have the motherboard outside the case on an anti-static mat. I disconnected everything from the motherboard and left only the CPU.
I plugged the 24pin cable and tested it again. It turns on for half a second and turn off, and in that moment I can hear a very low hiss, which seems to be coming from the PSU or from the motherboard. The hiss disappears after about 3 seconds.
If I plug the 8-pin cable from the CPU, the motherboard gives a quick, almost imperceptible blink. There is no time for the lights to turn on properly.

PS: the green light remains lit.

I'm thinking it might be short on something. I am wrong?
 
#4
A bad capacitor can give out a hiss and being that your PSU powers the other system ok the problem looks to be more like the MB, bad caps info here there are pictures to the right at the link which will help you identify any possible bad caps on the MB.

To do a barebones test properly you need to connect the 24-pin EATX power connector, the 8-pin ATX 12V power connector, the screen to a video port on the MB, a keyboard and one stick of RAM in the second slot away from the CPU ( Slot A2).

If the behaviour is the same with the set up as described above I suspect that you have a bad MB, the only things that could short out apart from the MB are the CPU and RAM and being that you have test both in another MB along with the GPU & PSU and they each work it only leaves the MB.
 
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