Question PC powers on for 4 seconds then shuts down ?

[zSkyer64]

Hello, I have a PC with Gigabyte GA-H81M-S2PV motherboard that only powers on for about 4 seconds then shuts down, starts back up and does the same thing, over and over again ?
I've taken out the GPU, RAM, cleared the CMOS, reseated the RAM, tried with another PSU, even took out the CPU and it still won't do anything, not even a beep, just powers on for 4 seconds then turns off ?

And I have another one, the exact same motherboard, it stays on and does a weird beep every 0.5 seconds, repeatedly, and doesn't stop until I power it off. (

View: https://youtu.be/nFuiz1aP29k
)

Please help.

 

[rgd1101]

full system spec? include brand and model of the psu

was it working before?

 

[zSkyer64]

full system spec? include brand and model of the psu

was it working before?

The PSU I used before was a RPC 55000C, 600w psu, 4GB Ram, Intel i7 4790,
And yes it was working before, I just tried to turn it on now and suddenly it started doing that.