No backlight / LCD troubleshooting

Hi all!

After water damage to my Macbook Air in China the logic board was partially repaired so the laptop now boots but I have no backlight or startup sound. I just replaced the entire logic board with one I bought from eBay (little crusty looking, used etc.) and still have no backlight. Before I turn that board and request a replacement;

1) What are the chances that the used board also has a backlight issue?

2) Is it at all common for the backlight itself to “burn out” following water damage to the board?

3) Is there a simple way I can test the backlight to either diagnose our rule out any problem with the screen assembly?

Here is an image of the LCD connector schematic in case it's of any help.

Cheers,

Tom