Hi njoka,

Please connect an external monitor if available and let us know how the display behaves.

it works fine on external monitor,on it's lcd it shows nothing,how can i do next.

Hi njoka,

This indicates there is an issue with the LCD screen, Please use the link to check the warranty status of your system.

http://dell.to/Mbe3zg 

Please punch in the system service tag or express service code and click on submit and you can check for the warranty status.

In case your system warranty has expired please contact the Out of Warranty department 1-800-288-4410 (U.S.Customer only). In case you’re from different region please get back to us.