pc doesnt start.

[fufijs]

So i just get my new pc built by my self (ive built couples computers before so i know these things)
specs
mb - asrock z370 killer sli
cpu - i3 8350k
cooler - corsair H45
gpu - evga gtx 1060 sc
ram - 8gb Corsair vengence 2400mhz
psu - 550w corsair VS
however when i try to turn it on, it starts for 20seconds or so, all fans spin, etc but screen is black and after those 20seconds it shots down, however after 5more seconds it turns on by it self and like this it keeps repeat it all over and over again, shuting off, turning on.
Ive read that it coud be caused by damaged ram,mobo or if my cpu pins are bent, i did check my cpu its all fine, prehaps it might be caused by damaged mother board or ram? but all the parts were brand new. Any suggestions?

 

[_Glitch]

DOA is rare, but it does happen. We can quickly rule out the RAM.
Install only one of them and see if it happens again. if it does, try the other module. If it still doesn't work, try another slot.
Still a problem, the issue is not RAM related.

 

[_Glitch]

Ohh, and have you remembered the CPU 4/8pin cable?
I just remembered i had a problem similar to yours because i forgot that one time.

 

[johnb35]

Make sure you have the correct amount of standoffs and they are in the correct spots. Could be a grounding out issue. You can also try building it outside of the case to rule that out.

 

[fufijs]

DOA is rare, but it does happen. We can quickly rule out the RAM.
Install only one of them and see if it happens again. if it does, try the other module. If it still doesn't work, try another slot.
Still a problem, the issue is not RAM related.

I have only 1x8gb module and i tried in all 4 ram slots..

 

[fufijs]

Ohh, and have you remembered the CPU 4/8pin cable?
I just remembered i had a problem similar to yours because i forgot that one time.

I pluged in the 8pin cpu cable dont worry

 

[fufijs]

Make sure you have the correct amount of standoffs and they are in the correct spots. Could be a grounding out issue. You can also try building it outside of the case to rule that out.

I did take out the motherboard and assembled it all together on a carboard box.. but still same thing i turns off and than on. So i assume its not the standoffs

 

[ANNR]

I just put together a pc recently and it didn't start at all even though I plugged in the 8pin power for the cpu. I tried pluging in the 4pin instead and it worked. If your 8Pin cable split into 4 x 4 pins? if it is, make sure the pins match the wholes and try that. Not sure if this is clear..... not sure why my worked with 4pin and not the 8pin....

 

[Estavio]

It has to be a problem with the PSU,
not enough power is consumed, check the cables, use a video on youtube on how to do so, and try not to turn the pc on with this problem, it may cause a serious problem to each one of your components.

 

[_Kyle_]

not enough power is consumed

Not enough? Wut.

 

[Calin]

I did take out the motherboard and assembled it all together on a carboard box.. but still same thing i turns off and than on. So i assume its not the standoffs

I think it's the motherboard. I have had a couple of boards go bad in the past, and the symptoms were similar, but there's no way to be 100% sure without checking it with a different CPU and RAM. Take it to a local store and have them test it.