It works!
I was very sad and angry with myself for not reading the manual first and I left my computer for some hours.
Then, I came back and when I moved the module the backlight turned on!

It was a problem with the cable!

Thanks a lot

I plugged my LK204 to the unmodified 3.5 inch floppy drive's cable.
After that, I readed the manual and I found that I should _not_ do that, but it was too late.

Then, I modified the cable (replaced the yellow cable with one of the black ones) and It didn't worked... After re-reading the manual I ...