As it's OK with an external monitor, the problem is most likely the backlight. If you can see a dim screen display when shining a light on the screen, the backlight power supply (inverter) needs to be replaced.
XPS M1530, Windows 10 TH2 Pro 32-bitInspiron E1705, Windows 10 TH2 Pro 32-bitDimension 9100, Windows 10 TH2 Pro 32 bitInspiron 660, Windows 8.1.1 - 64 bit Compaq DX 4370G, Windows 10 TH2 64 bitAsus T100 Tablet, Windows 10 TH2 32 bit
Thanks for the response.
Unfortunately, do not see a dim display, even if a flashlight is directed to the screen.
If I make the room completely dark, the backlight itself is visible, even though nothing appears on the screen. This is similar to if the computer is on standby.
Think of it like having a TV on, but with the cable box turned off.