Sometimes the A/V out pins can get bent, you might look at them with a magnifing glass. That happened with my PS2. Check both the external pin on the A/V cable and the internal pins on the console itself.
I've tried that, and nothing.
When this whole thing started, the picture on the screen was green, witch I understand it is a protection thing that Sony put on the Ps2 to prevent piracy when playing movie DVD's ( I haven't played any of these DVD's ). After the green screen, the picture got darker and darker and finally the sound and image disappeared. Is it possible that these two things to be related?