Hi gal0s11 -
I also think there is a probability that the PSU is faulty and it's worth to try even a generic one if this resolves the issue
On the other hand -
From the symptoms you've mentioned, it could also be the settings on the BCLK, Memory, iGPU and NB frequencies/voltage. When I overclock my rig via BIOS and incorrectly made some settings in these parameters, I sometimes get the symptoms you mentioned. I also have a Gigabyte FM2 A85X mobo although an ITX one
Could you try this then -
Stick with your Windows 7 64 bit OS
Apply the official chipset and video drivers for Win7x64 from Gigabyte's support site from here
Select 'Save & exit' menu
Select 'Load optimized defaults'
Select 'Save & exit setup'
Run your Solid works, Mine craft or anything VGA intensive
If your rig responds positively to the above and becomes stable. You could then -
1) Install CCC ver 13.9
2) Then apply memory XMP via BIOS
Please do tell us if you need help to do these couple of tasks
Do come back and tell us how your rig responds to the above