No backlight dim screen

Hello fellas, I'm having a bad problem with my g2 vs980, it seems I have no backlight and my phone is only running off LCD light alone. Brightness is the same from 0 to 100 percent. Can barely see screen in any daylight, only inside and at night, outside in daylight it almost appears black, any way to fix this issue?help greatly appreciated!! Thanks in advance

Xperia Z3-Black backlight only,no image.

Hello. I got this Z3 with a broken screen, when I got it it had only black backlight, no image, but the LCD cable on the bottom was cut, so I thought that was why it had no image.
So I replaced the screen with a new one, but the issue remains, no image, only black backlight.
Tried restoring the software with Sony PC companion, updated to latest version, but it didn't help.
The phone boots fine, touch works, I can select options and sometimes I even get audio readouts of what is on the screen, just no image.
Is this a dead motherboard or something else? Because I went through a couple of new screens, none worked, so I'm out of the ideas.
I haven't encountered a case like this before, the screen either works or doesn't, the fact that the touch works and I have backlight puzzles me. No backlight or no touch issues are a common case to me, but this is a new one.
Can someone help here?
Thnx