monitor screen goes black

it just started happenening and its not on screen saver mode. I move the mouse and the screen is still black. I turn off the computer and turn it back on and its still not working then i turn the computer off and on again and the monitor works for about a minute then it goes black again. i tried another monitor and it worked for about a minute then that one too went black. so it it a problem with the motherboard on the computer

Since you tried another monitor and the same thing happened, it's probably the video card or onboard video, whichever you have. Or it could be the monitor cable. Try a different one.

And try removing the graphics card and gently cleaning all the contacts with a pencil eraser.