I need advice here,

When turn ON my Aspire 4520 screen is totally blank but when I connected to ext monitor it show my windows desktop (in ext monitor).

I think problem with my aspire lcd screen. I read at service manual and I do what they suggest to reset to system default at the bios.

After save bios to system default, disconnect ext monitor and reboot, the display come back in my aspire screen as normal. But when I totally shut down and turn off the system the display disappear again.

I already doing above step 2 -3 times and the result still same.

Any suggestion what to do next