Pc turns on and off repeatedly in 3 second cycles

[kmbecker123]

I just got new motherboard today because my old one broke. When I put my pc back together it started turning off and on again repeatedly. The specs on my pc are as follows.
Motherboard
Ga-z97-hd3
Cpu
I5-4460
16 GB ddr3 ram
GPU
Amd rx 550
HDD
Sata 1 tb
460 Watt Psu

I tried running the system bare bones and it still did it.

 

[Grugbug]

Your old mobo broke, what broke?
What is the make model of your PSU?

 

[kmbecker123]

I have no idea it is a stock one that came with my prebuilt. It is the only part I have left of that prebuilt

 

[kmbecker123]

I do not know what specifically broke on it but it is a 10 year old motherboard.

 

[rgd1101]

go thru the check list http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

 

[kmbecker123]

RIP that explains it, my old psu is not compatible with my current motherboard since it isnt modular. The cpu power cable is the wrong one for my motherboard. I feel stupid.