I have a Samsung plasma 42 inch tv it comes on and show good but after a few minutes it starts to make a scratching sound and then a popping sound even if only the video connector is connected.

SOURCE: black vertical line on p42w34p plasma

could be a loose ribbon cable on a buffer board, or one of the buffer could be going bad

SOURCE: Scratches on my plasma tv

your stuck with it, no way to erpair a scratched screen

SOURCE: 42 inch LG Plasma TV - Lost picture

ysus pcb that supplies voltage to the panel is faulty

SOURCE: 42 inch LG Plasma TV - Lost picture

Our LG 50" plasma tv screen went black after a popping noise but still had sound, after great diliberations decided to take the back off and have a peek!
We unplugged the tv and tested the fuses (there were three we could see) one had blown, the one on the left as you look at the back of the tv it also has one above it. We wrote the code/seriel number down and took the fuse to the electrical wholesalers Maplin and bought a pack of 10 fuses for £1.29 replaced the fuse in the tv and everything now fine!!!!!!
Hope this might be of use to anyone whose lost the picture after a loud popping/snacking noise but still has sound.

SOURCE: 42 inches samsung plasma screen with sound and without image

Check this link to find the LJ41-02759A board for your TV. These boards fails quite often and the TV will power ON but with the same symptoms as yours.