Hello. I have problem with my LCD. Before repair screen showed up for a moment when lid was at 45 degrees. At 90 degrees there is no backlight. After few tries doesn't show at any degree. The flex cable from LCD backlight was broken (maybe make some short circuit). I've replaced whole LCD, and it still doesn't work. What should I check first to propertly diagnose and solve my problem? There is no image on external LCD. No sound, nothing. My mainboard is 820-00875A (nyks 94v-0 nm19).