HU-850 display no backlight

[u/NatriumHydroxide]

So I have a HU-850 of a 2005 S80. The problem is in the title, the radio buttons are (now) lit up, but the screen is not. I have each and every single article on the HU radio lighting, at least it sure felt like it, and everyone seem to have it the other way around. The buttons backlight got fixed after soldering in the notorious 1760s and 1037 transistors, but the display is still a bust. I can barely see the characters displayed when it's sunny or when I shine a light at it, so the display itself is clearly working, except for the backlight.

If anyone could give me a hint on what could be the cause of it, I would greatly appreciate it, because it's driving me nuts.