1, loose memory and graphics card are the most common reasons for computer black screen. Solution: disassemble the main chassis, plug in the memory and graphics card again, wipe the golden finger with an eraser, and then plug it in again or change the interface. If you don't know how to disassemble the computer, I suggest taking it to the computer shop for repair.
2, it is also possible that the CPU cooling fan is broken! This situation is generally that the computer can still work when it is turned on, but it will crash and the screen will be black in a moment. Solution: Replace the CPU cooling fan and test other hardware devices.