Kobo Clara HD -

One of my Kobo Clara HD's is no longer booting. (I have three now)

I think the screen is broken, since it has some lines on it that don't go away.
Maybe broken when opening the case. I read that sometimes there is too much pressure on it while opening. Not sure though, since I was really careful while opening it. :bam:

Anyways.. to rule out that the Kobo is broken, and it's just the screen, I tried to boot t he Kobo after adding in /.kobo/kobo/Kobo ereader.conf the following:

[DeveloperSettings]
AutoUsbGadget=true

Now, when only the PCB is connected to USB, without any other of the hardware (so no screen, no battery, etc) the LED turns on like usual, but there is no USB device/mount point created when I turn on the Kobo.

So, what does that mean? Did my PCB die and that is why it is not booting?
Or does it check during boot whether there is a display and other hardware connected and halts during boot?

How can I rule out what hardware is causing issues?
If it is just the screen that is not working, I will order a new screen, but if that is not the issue, I will be stuck with a screen that won't be used :knife:

(microSD card is fine btw, this image is now in use on multiple Clara HD's.)

What to do, what to do :sos: