there are two cables (the display cable and the inverter cable), and they work independently. If the inverter cable is bad then you should still have a picture but it will be real dim since you don't have a backlight. If the display cable is broken, you would just have a white screen.
If you are not getting a picture at all it is usually going to be the logic board. It could possibly be the LCD but that is rare for them to just stop working at all.
I'm quite sure about the logic board because i've tested with an external monitor and I have no image on it too.
My only doubt is: with the logic board trouble should the backlights work or they are off due to no images data?
I've tested both inverter and flat data cable with a multimeter and them seems ok.