HP ZXseries lcd screen stays black

[verdugo135]

Ok so about a month back my lcd just stopped working. It has a lit background but it stays black. I called hp and they had me do some troubleshooting but it didn't work and they said my display was no good anymore so we left it there (I didnt want to pay all that money to fix it). About 3 days after that it magically worked again but one day it seemed like it was trying to go out again the picture got real grainy for a second then it went back to normal. Now I'm back where I started. I've tried everything, when I hook up an external monitor it works so it has so be lcd related. Any help/advice??