My computer boots up but the screen is blank

Hello,
i have has my computer for about a year and i decided to change the mother board
the new mother board has no video output so i tried one of my video cards.
so my computer boots up the the screen is blank.

i have checked the screen on my other computer and it works so it is not the screen?
but the video card works in a different computer so that leaves me completely confused

thanks,
dylan