I have an acer aspire which seems to be on but the screen is all black. It lights up for a second only to display a no signal

If it is still under warranty, then you should contact the manufacturer.

If it isn't under warranty, and this is the attached display, then you will need to open up the laptop and make sure the ribbon cable that connects the display hasn't been pinched, damaged, torn, jarred loose, or completely disconnected.

If none of that resolves it. Try turning off the laptop, connect an external display, turn on the external display and then turn on the laptop. Can you see your desktop on the external display? If yes, then your laptops display may well need replacing. If you can't see anything even on the external monitor, then your graphics card may well need replacing.