Suddenly, Sound But No Picture

Bad capacitors on your power board. Remove the rear cover and check for swollen capacitors. If they are swollen, you can de-solder the bad ones out, and solder new ones in.

Needs new main board, cheaper to buy new tv. Unless you have warranty.

Possible failure of the VERTICAL SECTION of the deflection circuit. It is possible that the areas related to the vertical circuit is checked , check for weak capacitors near the output vertical drive. Also a faulty vertical coil- deflection coil- can result in half picture.
A vertical signal test can confirm.

the sound suddenly stopped working on my Viore 42" plasma.

Check to make sure its not muted, if not then your main board most likely has failed

possibly the signal/tuner board or the input board depending on what the model number of the set is.

The first thing to check is the connections to your source. They can easily become loose and/or corroded over time.

sony has problem with bad picture tubes as well as flyback transformers .if you have shorted hori output then replace it if set shorts it out again your looking at bad flyback transformer as well as maybe leaky tube.

You apparently have a high voltage arc. Possibly the anode lead to your picture tube. Also the flyback transformer could be arcing. If you're not experience with tv repair, you need to have a tech check it for you. The circuits operate at very high voltage and if you get into it you can get a possibly fatal electrical shock. Be careful !!! Stargazer

possible shor in the jungle ic that handles the video.