I worked on a Lenovo T420 that had a backlight issue. I checked the inverter, that seemed fine, so i started checking fuses around the lvds connector and found that the F7 fuse was blown. I replaced it, put everything back together enough to test but when i started the computer, it won't post anymore ... 1 long beep and 2 shorts beep means a lcd assembly problem or a ram problem or a bad motherboard. So i tried without the screen connected, same issue, tried different ram and slot,still no luck. So i took it apart again and checked F7 again and found that it blew again ... I don't know what causes the NO post issue, it was working fine before. Can't believe that is related to the fuse replacement but I'm still new in repairs. Anyone has a clue ? Thanks