Do a real reset...
Also change out the video cable (hdmi?) & try different ports, make sure it is not the cable & make sure it is not just the one port... The other ports could be fine. Also try a different input device like a DVD/bluray player, a PC whatever.
Is the tv hookup to a surge protector?
If you have a can of compressed air, clean the ports 1st, then test the 1 inquestion port & the others... It could be just dust getting into the hdmi(?) port or into the hdmi cable end, maybe.
I have a 42" Panasonic plasma hdtv model # TH-42PX75U
I turned the t.v. on and the picture was fine, after a few minutes it went completely white, still had sound. Next I unplugged the tv for a few minutes and tried again, same thing.
Any ideas what this is? Maybe I'm better off donating it to the curb.
Any help would be great.