# PC Won’t start up with CPU Power Plugged in



## iamavenue (Feb 18, 2021)

My PC randomly shut off a night ago so I gave it a night. I went to turn it on after but it only lights up for half a second and doesn’t start. I unplugged the CPU power cord and then it starts, but you can’t do much without that.

Specs:
Mobo: MSI MPG Z390 Gaming Edge AC
CPU: i5-9600kf
GPU : MSI GTX 1660
PSU : EVGA 650w Power Supply
16gb of DDR4 Corsair Vegenace Ram

any help?


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## Peter1986C (Feb 19, 2021)

iamavenue said:


> unplugged the CPU power cord


How would it even boot then? Or I misunderstand something here 

I suggest that all parts have the required power cables attached, turn off the switch from the PSU and then turn the PSU switch on again. Then proceed to power up the computer. Please let us know the results.


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## iamavenue (Feb 19, 2021)

Peter1986C said:


> How would it even boot then? Or I misunderstand something here
> 
> I suggest that all parts have the required power cables attached, turn off the switch from the PSU and then turn the PSU switch on again. Then proceed to power up the computer. Please let us know the results.


It doesn’t boot up to windows, but things like the fans+lights will start up. I already tried the PSU switch, no luck though.


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## Caring1 (Feb 19, 2021)

iamavenue said:


> It doesn’t boot up to windows, but things like the fans+lights will start up. I already tried the PSU switch, no luck though.


When you turn off the PSU, leave it for say 30 minutes to drain all power and allow it to reset itself, or hold in the front panel power button while it is switched off.
Try another PSU if you can, beg, borrow or steal buy.
Try removing all Ram and booting.
Remove the CPU to check the socket and pins.


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## micropage7 (Feb 19, 2021)

i agree you need to check from the power cable then the PSU first


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## thesmokingman (Feb 19, 2021)

What's the cpu power cord to the OP?


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## RJARRRPCGP (Feb 19, 2021)

I suspect faulty MOSFET(s)!


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## twicksisted (Feb 19, 2021)

Faulty motherboard, Faulty CPU or Faulty PSU

Test each to isolate the issue.


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## iamavenue (Feb 19, 2021)

twicksisted said:


> Faulty motherboard, Faulty CPU or Faulty PSU
> 
> Test each to isolate the issue.


is there a way i can test these without completely different parts? I can’t get different parts right now to see which one it is


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## twicksisted (Feb 19, 2021)

iamavenue said:


> is there a way i can test these without completely different parts? I can’t get different parts right now to see which one it is


Not sure to be honest, I would swap each part out to check if they were at fault to narrow it down, starting with the easiest part and working my way round to the motherboard which would take the most effort to swap out


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## biffzinker (Feb 19, 2021)

The main board or power supply would be the two worth your time troubleshooting. CPU’s rarely up and die.


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## Zach_01 (Feb 19, 2021)

iamavenue said:


> My PC randomly shut off a night ago so I gave it a night. I went to turn it on after but it only lights up for half a second and doesn’t start. I unplugged the CPU power cord and then it starts, but you can’t do much without that.
> 
> Specs:
> Mobo: MSI MPG Z390 Gaming Edge AC
> ...


What kind of EVGA 650W is this, and how old is it?
For me is either PSU or the board... Some kind of short circuit maybe.

Can you measure the volts from every cable on that EPS CPU cord when pc is running?
1. Unplugged
2. Plugged

Between yellow and black it should read +12V. If you can do this, test all of them. If all of them have the same color then see below the EPS-12V


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## iamavenue (Feb 24, 2021)

twicksisted said:


> Faulty motherboard, Faulty CPU or Faulty PSU
> 
> Test each to isolate the issue.


I tried a new PSU, still no boot with cpu power plugged in.


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## Bones (Feb 24, 2021)

The "Blink" taking place when you try to start it indicates it's going into protect mode, hence the blink so you definitely have a problem. I'd have to say most likely it's board related but could be something else.



twicksisted said:


> Not sure to be honest, I would swap each part out to check if they were at fault to narrow it down, starting with the easiest part and working my way round to the motherboard which would take the most effort to swap out


This is the way to do it.


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## Caring1 (Feb 24, 2021)

Check the cooler isn't loose as it could be thermal protection shutting it down with the CPU power connected, also if that is fine it could be thermal paste on the pins, this would require you remove the cooler and CPU and check the socket.


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## iamavenue (Feb 25, 2021)

Bones said:


> The "Blink" taking place when you try to start it indicates it's going into protect mode, hence the blink so you definitely have a problem. I'd have to say most likely it's board related but could be something else.
> 
> 
> This is the way to do it.


I swapped out the PSU, and there was still no luck and just the blink. Do you think it’s the board or the cpu at this point. 
I inserted a picture of the cpu socket with nothing on it anymore... Anything look out of the normal?


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## biffzinker (Feb 25, 2021)

iamavenue said:


> I inserted a picture of the cpu socket with nothing on it anymore... Anything look out of the normal?


Socket looks fine


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## iamavenue (Mar 7, 2021)

I purchased a new PSU, no luck. I purchased a new motherboard today, still no luck. CPU at this point or what?


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## biffzinker (Mar 7, 2021)

One of the RAM sticks may of died.


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## iamavenue (Mar 7, 2021)

biffzinker said:


> One of the RAM sticks may of died.


Tried booting with one ram stick each, no luck.


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## FireFox (Mar 7, 2021)

iamavenue said:


> CPU at this point or what?


New Motherboard/PSU, Ram sticks works then i assume that CPU is the culprit, maybe try it outside the case, GPU is working?


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