Notebook Boot and Lockup

Hi everyone,

A friend of mine broke the pin of his ac adapter which get stuck in the power port of his laptop and gave it to me for repair. I dismounted the back of the laptop, removed the pin from the port, added thermal paste on the cpu, cleaned the fan, and bought him a new genuine ac adapter.

Few weeks later, his laptop shutted down while working (he couldn't tell me if it closed properly or shutted down immediatly). At reboot,  he was prompted to do a bios update due to bios having been corrupted, which he did.

The update seemed to run fine, but after that , Windows refused systematically to boot and bsoded  with "critical process died" (right after the HP loading logo).

Having access to the uefi bios and diagnostic interfaces I did the following :

* run every diagnostics with no errors

* tried to boot Windows in safe mode -> bsod

* tried to start various recovery tools from uefi menu -> bsod

* booted with success to a linux live cd, and checked the hdd

At this point, I tried to update the bios again , the process seemed to run fine again, and now,

the laptop screen remains blank at startup. I have already tried the following with no success :

* Pressed ESC at startup

* Pressed F8 (low video resolution)

* Power resetting (holding the power button for 20sec)

* Boot to bios recovery (power button for 3 seconds while windows key + B pressed) with and without a usb recovery key

* CMOS clear (power button for 3 seconds while windows key + V pressed) :doing this make the led on the f6 key blinks every 1sec.

* All of the above with battery removed

* All of the above with battery, hdd, ssd, wlan disconnected

* All of the above with the ram stick swapped to the other slot.

* All of the above with a monitor plugged to the hdmi port (with pressing on  secondary display key  [F4])

The laptop do not emit  beeps nor blink patterns.

I didn't find the cmos battery on the motherboard to remove it so I guess that's the main battery's job.

I think I bricked the motherboard , but I'm not really sure, Did someone had resolved similar issue ?

Maybe I can flash the bios chip directly ? or physically reset the cmos (but I can't find it on the board) ?

Also I wonder how the bios bin would have been corrupted. I checked the mobo and it has no trace of damage.

It is me when I first dismounted the laptop ? Or could it be the new ac adapter that is disfunctional ?

Thanks.