No signal monitor....?

I had this pc a while back and one day i went to turn it on and bam no signal.. to the monitor.. so I'm like okay.. Video card went bad of course is the first logic no signal to the monitor.. what gives the monitor signal is the video card.. and I got another video card a 2nd hand video card and i Put it in the AGP slot.. and same problem.. so i'm like 2nd hand maybe it was broken already.. so i went n bought a new one.. but same problem.. so basically.. I dont get a signal to my monitor and is NOT the video card :) the computer does turn on and no beeping sounds after I tried it with my TV instead of the monitor but same problem