Okay, long story short.
This started as a simple screen repair. The customer had sat on his laptop, and the screen was cracked. I swapped the screen, and it worked.
A week later, it has a new problem. No chime, no post, vertical lines on screen and then nothing but backlit black.
Okay, so probably not a screen problem then, seeing as there's no post. I try an external display, nothing. So it's gotta be the board, most likely cpu/gpu (due to artifacting), right?
EVERY LINE TESTS NORMAL.
okay, so I swap the board anyway, because everything's tested normal but ''maybe'' the power rails got temporarily bridged and it fried the cpu or something (i know its unlikely, but im just clutching at straws at this point).
no change. Fans come on full power, no post, vertical lines on screen, and the light on the charger stays off.
WHY