See if any show you how to swap screens or turn on/off the LCD or external. If that doesn't work, the laptop usually needs repair. Get estimates as laptop prices have eroded over time.
I have a Samsung NP300E5Z laptop windows 10 and when I turn it on the screen doesn't show anything and remain black. (I've connected it to an external monitor via HDMI and it works perfectly) I have changed the laptop screen and cable but still didn't work.
If you have encountered this problem and solved it please let me know how.

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