Backlight troubleshooting

There's basically three reasons why the backlight won't turn on a) wrong dtb (which can't happen when flashing a new image) b) cable slit out slightly (see below) c) broken backlight (although we've not seen this yet).

If the ribbon cable is not parallel (upper part further out than the lower part) then the back light won't turn on. This can happen when the upper left of the panel is tilted to the right.

@david.boddie mentioned the nice trick to use a bright light to see if one can see phosh's arrows at the bottom of the screen