Black screen still appears after clean install of W10

Hello everyone.

So, yesterday I was playing a game for about an hour and after about 30 minutes I had a black screen. I restarted the PC and everything was OK. Today in the morning I started the PC and after 3-4 minutes of using it there was the black screen again, with apps and everything clearly working in the background, no cursor. For last 16 hours I tried to do everything to fix it. At first I thought it is a software issue - I managed to start Windows 10 in emergency mode, it had a really low resolution. When I disabled or rmoved BOTH screen drivers and GPU drivers Windows started in a normal way with a very low resolution and after 4-5 seconds there was black screen again. Other then that, nothing worked and I tried about 20 different things. I decided to format both SSD drives and install a clean Windows 10. I did that and it didn't help. I also tried to reinstall it again on the other drive and nothing changed. I tried using a different screen that works fine - nothing. I tried different socket, nothing. I tried changing different settings in BIOS, nothing. I tried disabling fast boot, nothing. I tried removing everything that is connected (keyboard, mouse, speakers etc.), nothing. I tried rolling back graphic and screen drivers, installing old ones, installing the newest ones, nothing. I opened the PC and examined all the parts, one by one, nothing. I tried disconnecting both drives and starting the system with only one of them connected, nothing. I started to wonder if this might be a hardware or BIOS issue. I changed the graphics to integrated ones in BIOS and now nothing happens after the start - there is no BIOS, no nothing, the screen is completely dark...

I am literally hopeless. I cannot afford a new PC and I need this one to work - and I have already failed a deadline due to this problem and I might soon lose a job... What else can I try to fix it? What might be a nature of the problem?

Here are my specs:
RAM: Kingston 8192MB 1600MHz HyperX Blue CL9 (2x4096)
PSU: Be Quiet 730W Pure Power
CPU: Core i5 (1150) Intel i5-4670K 3.40GHz 6MB
MOBO: MSI Z87-G45 GAMING (Z87 3xPCI-E DDR3)
GPU: MSI GeForce GTX780
CPU cooling: SilentiumPC Fera 2 HE1224 (775/1155/1150/2011/754/939/AM3+)
2 SSD drives, both are new (less then one year old) from different manufactureres.

I built the PC in 2014, so it's quite old.

Hi,

Since you have your original PSU I would test with another one first. Your MB is all solid cap and TUFF component with good heat sinks.

The gtx 780 is approximately 8 years old and the rated power draw is about 220w.Its performance with newer games is "iffy".
Suggest you disconnect all power,remove the motherboard battery for one minute,then replace it.
Remove the gtx 780,check the mobo and card slots for any signs of discolouration and distorted capacitors.
If the gtx has active cooling,a fan,then gently blow on it to make sure the fan is working.
Only connect one monitor,mouse and keyboard and the ssd with the operating system on it.
Restart the computer,enter the bios and reset it to the default settings.
Shut down,restart and see if normal operations resume.
When fiddling with computers,it is prudent to use old fashioned methods.With pen and paper,write down EVERY thing you do,so backtracking is possible.

I would check the heat of the graphics card. I know that while playing games, my Radeons can get pretty hot and if I don't set the fans to spin manually, they don't keep up and I get a black screen much like you are describing. It's pretty common for a graphics card to black out when it gets too hot.

That is definitely one of the places I would check out.