Hi @techlord
Did you disconnect the battery from the motherboard when cleaning, you never said?
Connect an external monitor and check if there is a display on it when the laptop is turned on and booted up. If the external monitor works OK, then use a torch and shine it an an angle close to the laptop screen and check for any images. If you see them, (they will be very faint) then there is a backlight problem.
Normally the backlight power is on all the time when a laptop is turned on and it is turned on and off ''in the LCD panel'' by a signal voltage from the BIOS (and can also be from the OS to the BIOS) depending on requirements. You said that the lid sensor broke off the motherboard. It is the lid sensor that tells the BIOS whether the lid is open or not so perhaps it thinks that it is now shut so therefore the display is turned off.