Lenovo Vibe P1 backlight is very dark

After the screen has been cracked I have order a replacement and I did replace it with a new one but now it get cracked again and I have to replace it with another one, but before I replace it the screen back light become very dark I can see the screen but it is very black, everything else is working fine (the touch, the mobile) I checked with another screen and it is the same, still black, it seems to be the "backlight inverter" in the board but I have no experience with that, any one can help?