Have a 42" Sampo plazma
Before we proceed, i would like to share few details. The life of plasma totally depends on the usage. For a normal user it is anywhere between 10 - 14 years. There are few people who have actually used it for even more years depending upon usage and care. However, as i have no idea whether you have sparingly used it or the condition, so i would take an average life span.So, as a normal user you are left with less than 4 years before you would see other parts worn out. These are made in such a way that they mostly require replacement than repair, so cost is always a factor before getting them repaired. There is a thumb rule - when the cost of the repair is more than half the amount of the product, buy a new one.If are experience in electronics, could read schematics and would be able keep precautions, then it's different - you could save labor cost. Unless it is better to replace it.
I am sure you must have checked all the connections to make sure there is no lose connection. As unplugging didn't help you, there could be few causes ranging from digital board, sustain boards and few more. The more probable cause is driver board failing. If you call a tech, it would be an expensive deal taking into consideration the cost of the new plasma TV's and age of the TV.
Note - As i cannot diagnose the TV, this information is purely based on what i saw on most occasions on the basis of the description you gave.
Let me know,if needed further assistance.
Hope i helped you.
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