This used to commonly be the little cable going from the inverter to the board. In 2014, this machine being six years out of production, it can be absolutely anything. The screen light, the board, the inverter board, the cable.
Also expect every one of those cables you find on eBay to be pulled out of laptops used for the past eight years and for them to be almost as dead, if not as dead already, as the cable you are taking out of your computer.
This is an absolute nightmare to fix in 2014 because all of the parts you will be buying are junk. :(