The cables from/to the motherboard (they can be defective in some way) and next we replace the motherboard.
There are some that want an engineer to diagnose such a laptop but the cost per hour is higher than what replacing parts cost. And if you follow the tech's flow charts, you see the advice given.
Hi. I've been having some trouble with my Toshiba Satellite L450. After starting the computer, the back light goes out after a few seconds. If I light up the screen with a lamp, I can still faintly see what's on it so the screen is still working. Closing the lid and opening it will make it light up for another few seconds. This happens regardless of software as the back light will go out even in the BIOS. I've tried to replace the inverter board with a new one (found one on ebay), but that made no difference. Since the screen is actually lighting up the back light has to be still working and since the inverter board wasn't the problem, I'm thinking that the screen is getting an order to shut off the backlight (as if the lid was closed). Does anyone have some tips?