Uhm, try that thing where you hold the PS button on the controller for like 5 seconds as it starts up. It's supposed to reset the video settings to match your tv. If they're wrong, you've got no video or anything. That's the thing about PS3. You can't just plug it into a tv second hand and expect it to work flawlessly, you need to set the video settings up first.
So try that and then tell us what happened.