If this problem happens and trying to fix the device, you may first try to replace the LCD module, to easily determine if the white LED's mounted at back of it is already been damaged or not.
If after installing a new LCD but still it shows a dark screen display, you may then refer to the solution below and locate those certain components for check up and for tracing the display backlight LED's connection line paths.
Trace each of the LED's connection line paths from the LCD pin connector down to where it is being connected in a certain capacitors components.
Since only the LED's positive supply voltage have a ideal spots where you can check it connection line path.
While the LED's negative supply voltage is connected directly to the GAZOO chip, so there's no way out that you can check its connection down to the solder ball of the chip.
You may tend to rework the GAZOO chip if the LED's positive supply is working okay and if the problem still exists.