Clevo P751DM black screen after boot.

Hi guys, my laptop just went down. I'll try to keep it tight and clear, please keep in mind i'm a semi-newbie. So the main question is:
How to diagnose if it's a GPU, CPU, mobo, RAM or disk failure?
specs:
CPU: Intel Core i5 6600K
GPU: Nvidia Geforce GTX 970m 6GB GDDR5
Memory: 1x8GB DDR4 2133Mhz Kingston HyperX
Disk: 250GB SSD Samsung 850Evo
How it happened?
Haven't noticed any weird symptoms before, just one day I pressed the power button and got the black screen, then after about 20-30 seconds it restarts itself and stays on with black screen. No BIOS loadup, no beeping, no Windows loadup, won't react to any key pressed on boot, keyboard backlit is on but function keys aren't working. Don't know how fans should act in properly working laptop, but they do turn on with low speed when certain parts (gpu/cpu) get heat. PWR led is green, power supply is operational and charges the battery with correct LED indication.
What have I checked?
- removed laptop battery and tried to turn it on only with power supply
- BIOS battery removed for 20 mins
- BIOS battery replaced with new one
- Checked power supply with multimeter and it has right voltage. I'm unable to check it "under load" (power/current consuption) because the multimeter I use has only 10amps fuse, and power supply is 11.8. And I have never done it before, don't know what size of cable should be used, to what pin should I connect it in a power socket etc.
- Plugged in an external monitor through HDMI cable
- Removed and tried to start without:
- disk
- gpu
- ram
- cpu
Only in one case something is changing - when I remove CPU. Few seconds later after it reboots itself fans turn on at maximum speed and battery/power supply LED starts blinking in orange, which (according to user manual) indicates charging any device connected to USB 3.0 port when laptop is turned off
Questions:
1. Does UEFI BIOS need a disk to be plugged in to start?
2. Should it bleep without GPU/RAM/CPU? If it's not isn't it indicating that BIOS(or mobo) is ****ed up? Do laptops even bleep?
3. If it would be GPU, is it possible to start without MXM card? Is there any trick to do that?
4. What's messed up in your opinon?
I'm all ears and hearing for any advices from you.

 

With the testing it's likely a bad motherboard, talk to your reseller.

 

I'd had same symptoms after failed BIOS flash (or flashing it revealed chip problem). Can you run fans at max speed (Fn+1)? If the warranty still applies, just RMA it and they get the MB replaced.