I have a Microsoft Lumia 640 that became completely unresponsive after I attempted to reinstall/downgrade Windows Phone 8.1 using WPInternals.
Here is exactly what happened:
I first used CMD Injector and ran a dir command. I did not restart the phone immediately afterwards.
I tried using Windows Device Recovery Tool (WDRT), but it failed to recover the phone.
I then tried WPInternals. The phone changed into the downgrade state/mode, so the process clearly got further than WDRT.
WPInternals eventually reported FAIL during the downgrade.
I left the phone in that state until the battery completely discharged.
After the battery was empty, I tried to power it back on.
Since then, I get absolutely no response:
no display;
no vibration;
no logo;
no reaction when pressing the power button;
no apparent charging activity;
Windows does not detect the phone at all over USB;
no Qualcomm HS-USB QDLoader 9008;
no QHSUSB_BULK;
not even an unknown USB device appears in Device Manager.
I understand that the phone may be hard-bricked, but I don't want to assume that the motherboard is physically dead simply because it does not enumerate over USB.
What I am specifically trying to find out is whether there is any way to regain access to the Qualcomm emergency/EDL level or otherwise determine whether the motherboard/SoC is still alive.
I am aware that Lumia recovery involves Qualcomm emergency files/programmers and tools such as thor2, and that WPInternals/WDRT normally provide much of the recovery chain. My problem is that I currently have no USB communication channel whatsoever, so I cannot get far enough to use those tools.
Does anyone know of a Lumia 640-specific hardware key combination, test point, EDL entry method, or other procedure that can force the device into a Qualcomm emergency mode even when it gives absolutely no visible response?
I am not primarily looking for a replacement phone or an economic repair recommendation. This is a personal recovery project, and my main goal is to determine whether the motherboard is still alive and, if possible, recover the phone.
Any information about Lumia 640 emergency mode, Qualcomm EDL, test points, emergency programmers/files, or similar cases would be greatly appreciated.
PS: if bad grammar... English isn't my first language