I'm sorry no one has replied sooner. Its difficult to determine what has caused the failure of your TV, but there is a diagnostic you can do, to if you want to isolate the possible circuit causing the problem (this is what a TV tech would first do).
You need to disconnect the AVC unit from the TV. Then, ensure the TV is turned on by the main power switch. Open this document attached here
, and follow the instructions. You press the sub-power switch for 5 seconds and the TV will run diagnostics - there will be blinks on the front panel power light. The blinks will be like 2 pause 2 (1 second blink for each blink, then a 2 second pause). Count the blinks, between the pauses and it will indicate which board is the likely problem.
To turn off the diagnostic, press the main power switch (turn the TV off).
The most expensive board to replace is the X or Y-sus boards, they run about $300 plus labor. Other boards are less expensive to replace, unless its the SDM board, as it is permanently attached to the Plasma panel and would require the entire Plasma Panel be replaced - which is about $500 plus labor.