No backlight on my screen

I have replaced the screen, replaced the cable to the screen, replaced the back cover for the screen. The screen still has no backlight. I can faintly see the screen if I shine some light on it. I read (in a nearly 20 year old article) that it could be the lid closed sensor, but I can't even figure out where that is. Or it could be the inverter, also can't find that, probably integrated into the motherboard these days. Any thoughts of suggestions would be appreciated.