My Zenith Z42P3 plasma TV, which is about 3 years old, has developed an issue. At times, the screen won't come on. The sound comes on fine, but the picture won't.

Hi

Thanks for using FixYa. As Plasma TV is a very hard working device so it produces lots of heat and around 75% issues in Plasmas are caused due to overheating. To start with you'll have to open the back of the unit and check for any bulged/bad capacitors on Y and Z-sus boards. As the sound is working fine so it seems that the power supply is fine, also check the control board for any bulged capacitors. You can click on this link to buy the parts. Please accept the solution if the issue is resolved or post a comment for further assistance.

Thanks
Rylee