Backlight doesn't work after replacement

I had to repair an iPod Nano 6g, the screen did'nt work anymore, it stayed black.

After some time staring at the screen, i saw that only the backlight didn't work anymore, so i thought it was just the lcd that was broken.

I replaced the whole screen assembly.

Now is the screen replaced, but it doesn't work too... I wonder what to do now, i hope i didn't spill money by replacing the screen.