Fx990-ud3 Rev 4 - won't boot, sometimes posts, sometimes black screen

[Ddosix]

Hello,

After using my pc for several years the computer won't boot. Basically it shut down a week ago and wouldn't boot. Black screen (power saving), all fans spin, CD rom works, video card sends signal to the monitors.

What I've tried:
Swapping ram and using only one sticks
Different psu
Clearing cmos
Taking out battery
Changing pci port for video card
Discharging mobo overnight + holding power switch for 30 seconds
Literally everything I could on the guides.

The board doesn't touch the back panel, all screws in the right place

Specs:
Fx-9590
Msi Gtx 970 rgb
Corsair 850w psu
Corsair vengeance (8gbx4) 32 gb ram
Liquid cooled with I believe a corsair
Windows 10

Sometimes it shows the gigabyte boot screen with bios options
Rarely it goes past it to rebuild windows but then shuts off
Rarely it tries to dual bios (rebuild a corrupt bios)
Almost always won't even show the bios screen (can't hear cpu running)

Last week after several shut downs and restarts it started working again for a week and then shut down yesterday with what seems like no hope

Something I noticed while in bios before it cut off was the bios settings showed .8 v vcore to the cpu instead of the 1.5v it requires (I think)  but most of the time I can't even get to the bios.

All wires plugged in properly, it worked for years.

Any ideas? Replace the motherboard?

[AgentFXA]

Yep, when vcore is unstable, and CPU/VRM temperatures are fine, it's time to replace the mobo

[Ddosix]

Ok so for people with the same or similar issues. I got a new mobo and the issue persisted (son of a bitch) but then I installed a $60 sempron chip I had laying around and it booted fine. So basically my cpu was s***ting the fan anytime it came under load causing the pc to sometimes boot past certain points and other times just s*** the fan. I don't have time to test the sempron on the other motherboard but I'm sure it would work and I'm too lazy to take the new motherboard out (I also like this one more).

Highly recommend the sabertooth r3.0 for the led displays while booting, seeing the cpu light light up and then immediate shutdown def narrowed it down.

[Ddosix]

Here is the full solution:

It was actually the liquid cooler which stopped working and then broke my CPU. I noticed it by installing a sempron 145 (gave me enough time to look at bios temps) and saw it climbing. Bought a new cooler and CPU chip and now the PC works fine.