Lenovo IdeaPad 510-15ISK - BIOS recovery doesn't work

[outsydeh2o]

Hello everyone. I have a Lenovo IdeaPad 510-15ISK with NM-A751 REV 1.0 motherboard and InsydeH2O UEFI BIOS, running (as far as I remember) BIOS version 0XCN36WW. The machine mysteriously got bricked after switching from UEFI to Legacy boot mode in BIOS Setup, which I have been trying to recover for the last week, trying numerous things and not succeeding with any of them.

What happened was, after switching to Legacy mode and saving changes, the machine restarted and showed the Lenovo BIOS logo as usual. However, after a few seconds, the screen suddenly went black. Ever since then, each time I turn it on, the machine does nothing other than spin its fan at normal speed for about a minute, then power off and on to do the same thing, basically being stuck in a bootloop until I force it to power off by holding the power button. During this process, nothing is shown on the screen, and the machine doesn't seem to respond to keyboard presses. Although, I can feel the LCD backlight lighting up slightly, meaning it likely tries to output video.

The last thing I've been trying to do is to get the Fn+R BIOS recovery method to work, assuming the BIOS is bricked. Using another computer, I successfully extracted the latest and only available BIOS (0XCN45WW) on the Lenovo website (using innoextract and extractor.exe) and opened the file with UEFITool to find out the crisis file name should be 0X_Crisis.fd (see attached Screenshot_1.png). I then renamed and put the extracted BIOS file on a 16 GB USB drive formatted as FAT32, and plugged it into the machine (using the USB 2.0 port that is on the same side as the power jack). Then, I power cycled the machine, and plugged it to an outlet while holding the Fn and R keys for about a minute. This time, the fans started spinning very loudly (at full speed), so I assume the machine has entered the BIOS recovery mode. However, there were no BIOS write beeps at all, and the fans started spinning down after another minute. I waited for about five minutes, then powered the machine off and on, and of course it was still dead like before.

Since then, I tried using many other file names (see attached Screenshot_2.png), using another 16 GB flash drive (also formatted as FAT32), creating smaller partition sizes (first 2 GB and then 128 MB) on the drive, trying the other USB ports, trying other BIOS dumps available online. Despite all this, the machine does the same thing every time, instead of flashing the BIOS and beeping rapidly while doing so.

Here are the other things I tried before trying BIOS recovery:

• Power cycling (tried it many times, holding the power button for between 15 seconds and a minute)
  
• Clearing CMOS (unplugged the power cord, then both the CMOS and regular lithium-ion battery and waited for 30 minutes twice. I also wanted to try using a jumper, but I couldn't locate any on the motherboard)
  
• Reseat the 4 GB RAM stick (Note: The machine has 8 GB RAM, but the rest of it is soldered on the motherboard)
  
• Reseat the LCD connector and also various other connectors on the motherboard (in case something coincidentally got loose)
  

I suppose there is nothing else left I can try and the machine is likely dead for good, but I wanted to ask here to see if I missed anything while doing BIOS recovery or anything else. I appreciate any help and thank you in advance.

Best regards.