\"No Signal\" when connected via DVI

There are three DVI connectors, two on the video card and one on the "mother", I connected a monitor to all three and each time it says "no signal". I went to buy a new DVI cable, but nothing has changed. I called the master, he said that he had never encountered a broken DVI connector on the monitor and that the computer had to be taken for diagnostics. Now connected via VGA, but it's generally slag. Can anyone give me some good advice or do I need to buy a new monitor?