1: no video output - be sure VGA is plugged into card installed in case not motherboard. the CPU does not support onboard video, only the video card.
2: incorrect resolution - not likely... but check dipswitch on IO board to be sure it's outputting the correct resolution for the monitor. (640x480) by the description of the rgb nosignal you describe.
3: computer failure - re-seat ram and video card and retest. swap ram if you have a spare to test with, it's not uncommon for the ram to go bad in these.
4: possible bad powersupply, but probable bad caps - check for swollen topped caps around the smaller heatsink and ram slots. if domed up, capacitors will need to be replaced and possibly dead board.