Everything else works. LCD backlight responds to light/dark on webcam so ALS is working. I have 5V both sides of D7720 / L7220. 5V at J4915. Tested FB lines for continuity back to resistors near U7701. Those resistors are zero ohms. R7747 measures ok. Tried forcing 3V to C7747 with R7747 removed. Replaced U7701. tested with new kb Backlight and 2 other used ones. Nothing. I'm lost.