I have a Hitachi tv and tonight the screen went

My tv did the same thing. I replaced the y-sustain board first and regained a faint picture. I read somewhere else that the y and z-sustain boards are common problems for plasma tv's. I replaced the z-sus board and the tv works just like it used to.

Usually it is the Y-sus that has the problem. This is one of the boards that sustain the picture on the screen.

For this particular issue, there could also be issues with the y-drives and Z-sus. The way to find out for sure is to take the voltages (Va, Vs, Vcc, etc) on the boards and matching them up with the specified values on the panel.