My e1705 started last week going dark from left to right. In my case, if I left the lappy turned off overnight, the screen appeared ok, but after 30 or so minutes started going dark again. I connected a secondary monitor (LCD) and switched from the LCD to the external, the video was fine. Then after leaving the computer on for about 24 hours, I switched back to the lappy LCD and it looked fine (but a bit dark). Again after 30 minutes or so it started getting dark again. I suspect the LCD died.
My e1705 screen is a Philips LP171WX2(TL)(A2) WXGA+ ... I have no idea what Dell would charge but the replacement online is between $117.00 and $176.00 depending on vendor. I've ordered a replacement online. Dell charges about $149 for an on sight repair but guess what... everything but the LCD and mother board are covered. In any event, after I change out the LCD, if it doesn't resolve it, then either the video processor or mother board is gone.
BTW - There's a good chance the fins on the heat sink for the video is clogged as well.