Black screen, speaker is silent, coolers are spinning, although before that everything worked. What happened?

Question

Iron

Thank you all in advance for your attention to my problem.
You can’t do without a backstory here, I apologize in advance ... Actually she:
I sat 2 days ago on a working and quite usable hardware:

• Processor: Intel core i3-3220
  
• Motherboard: Asus p8h61-mlx3 r2.0
  
• Power supply: Crown cm-ps500
  
• Video card: GeForce GTX 960 4gb
  
• RAM: 8gb ddr3 1333mhz
  

And I decided to replace the processor, and therefore the motherboard with a cooler, and RAM with new ones:

• Processor: Intel core i7-7700
  
• Motherboard: Asrock-h270m pro4
  
• RAM: 8gb ddr4 2400mhz
  
• Cooler: Deep Cool gamma 200t
  

I did everything carefully... Black screen, the speaker does not give signals, the coolers are spinning. He pulled out the RAM - the speaker is silent again, although it is already impossible to be silent here .... I poked it all for another 3 hours and decided to bring it to the service center under warranty, but here's the problem - While I was pulling the processor out of the socket, or when I just inserted it, I bent the legs in the socket - The case is no longer guaranteed.
So far I had to take it to a paid center.
Now the strangest thing - I put back my old CPU and motherboard with RAM in the hope of googling the problem - Same thing: Black screen, silent speaker, Coolers are spinning. This absolutely killed me.
The first thing that came to mind was that I connected the cables incorrectly and so on. I studied this process with 2 instructions, videos on YouTube and asked unnecessary questions to my friends - Bottom line: I connected everything correctly.
The second thing that came to mind was that the cables from the PSU broke during the installation of new hardware. He carried his old uterus and percent to a friend (the BP, respectively, is different and working) - the same thing. This finished me off ... But on his hardware I made sure that the memory, vidyuha, and SSD are working properly.
Guess number 1 - Motherboard. BUT after all, it was work 3 days ago ...
Gentlemen, who read it to the end, I would very much like to listen to your versions and guesses. I hope I have described the problem in sufficient detail. Thanks in advance for your work.

Answer 1

Hello, maybe the problem is in the memory, one of the ddr is bad, try to start with one of the non-failed ones.
Perhaps the uefi is bad