PC doesn't POST anymore (sticky thread checked)

[Dadapatata]

Hello.
In the last month i had occasionally a BSOD whenever the pc was inactive.
I decided i was going to change the HDD in a few months(as an analisys confermed it had some errors because of age).

The situation changed 3 days ago: in the morning i started the pc and (before booting) it automatically started to diagnose and repair the system(don't know why).
After that it restarted and the nightmare began;now the pc continues to restart every ten seconds while showing on screen the BIOS (without text).

Here are the parts of the PC

PSU:Corsair RM 750W
GPU:Nvidia 1070
CPU:Intel i5 3330
RAM:8G 2Rx8 DDR3 1600 U
MOBO:Gigabyte GA-B75-D3V rev 1.2

After some researches online i found out that the pc doesn't POST,i tried many things,included the ones that you gently provided in this thread
http://www.tomshardware.co.uk/forum/261145-31-perform-steps-posting-post-boot-video-problems

This are the results:
1)The manual doesn't say anything of importance
2)All the cables are correcly connected
3)I am doing breadbording on a non conductive surface
4,5)Checked,the results are the same if i use the integrated graphics or the old 950 or the 1070
6)I can't access the BIOS and i only have one stick of RAM.I tried all the 4 slots
7 to 10)OK
11)Ok,photo provided
12 to 14)OK
15)Breadbording so ok
16 to 21)OK
22)Tried integrated graphics,behaviour doesn't change
23)OK

Most importantly:
I cheked the mobo carefully,no signs of damage appear.
With only CPU installed,i hear a series of short beeps,with RAM also installed,no beeps are heard(remember that the mobo has integrated graphics).
POST beep is head only one time out of 20,even in this case the behaviour is the same(no boot).
I replaced GPU and PSU with the previous ones(changed them just to upgrade some months ago) but behaviour is still the same.

Here is a video of the behaviour:the CPU fan can't start in the first seconds and after 10 seconds the system automatically shuts down and restarts creating a loop.
https://www.youtube.com/watch?v=7ngQ0NMpqxY&feature=youtu.be

I also checked the CPU state and it appears undamaged(photos here)
http://imgur.com/a/zyPCE

My conclusion: PSU,GPU and RAM are surely good.With a probability of 90% the problem is the mobo,the remaining 10% is on the CPU.

Please tell me what is the problem or what i can do to discover it myself.

EDIT:Even without RAM inserted,the behaviour is the same.

 

[tsnor]

Many approaches. I'd guess RAM and order another dimm. Use only the new dimm, not the old one. If problem goes away try using both dimms. If problem comes back throw away old dimm.

If ram doesn't help then I'd get a new PSU and see if that stabilizes the situation. That should be free with your 5 year warranty.

If ram and PSU are fine then hit the MB, it might still be in warranty or it might not, 3 years.

Video was nice.

Good luck.

Warranty info for MB: Warranty Terms 3 years so you may be able to RMA, http://www.gigabyte.us/Support/Warranty/0
Warranty info for PSU: A five year warranty and lifetime access to Corsair’s legendary technical support and customer service http://www.corsair.com/en-us/rm-series-rm750-80-plus-gold-certified-power-supply

 

[Dadapatata]

Many approaches. I'd guess RAM and order another dimm. Use only the new dimm, not the old one. If problem goes away try using both dimms. If problem comes back throw away old dimm.

If ram doesn't help then I'd get a new PSU and see if that stabilizes the situation. That should be free with your 5 year warranty.

If ram and PSU are fine then hit the MB, it might still be in warranty or it might not, 3 years.

Video was nice.

Good luck.

Warranty info for MB: Warranty Terms 3 years so you may be able to RMA, http://www.gigabyte.us/Support/Warranty/0
Warranty info for PSU: A five year warranty and lifetime access to Corsair’s legendary technical support and customer service http://www.corsair.com/en-us/rm-series-rm750-80-plus-gold-certified-power-supply

Hey,thanks for the quick response.
I edited the post in order to say that the behaviour is the same even without RAM inserted so the RAM is probably not the problem.Regarding the PSU i have originally written that even with the old PSU the behaviour is the same so it surely is not the problem.

Tomorrow a friend should probably bring me some spare parts for testing,i will keep you updated

 

[Dadapatata]

When i can,i will try with other parts,thank you for tour assistance!