Why is my display not backlighting?

I'm looking for a schematic for the motherboard in my Lenovo 81UT003WUS. The motherboard part number is 5B20S42804. Have a no backlight situation, pretty sure it's the fuse but can't find it to check. HELP!! :) Problem started after screen replacement, perhaps faulty. Screen was installed in 2 identical computers to troubleshoot and now neither will backlight any screen. External display works fine and there is a dim image on internal display.