fn+f5 will toggle video output between internal, external, or both on your machine fn+f6 will turn the display blank, tried that? but it also says any key should restore it, but worth a try https://www.manualowl.com/m/Acer%20Computers/Aspire-5536/Manual/114414 page 6, hotkeys edit: you also have a HDD indicator LED, when you boot is it active??