The backlight is a LED wafer that slides in behind the LCD screen. It acts as a light source so you can see the LCD better. If you can adjust the LCD contrast and see the LCD blocks get darker then your display is ok, you just need a backlight. Telesis (
www.telesisgear.com) is great for backlights. I have ordered S950 and MPC60 backlights from them and had no issues. You might also want to make sure the problem is not your inverter (power supply for backlight).