Sorry, I do see where I missed that you said black once before. I missed it reading, I do apologize, I half way expected all these to be many colors so I guess my own presumption made me skip that.
All black is actually very bad, I was hoping they were colored as that would point to a possible circuit board problem.
But all black and the fact they did not change at all when you replaced the buffer and the y would point directly to a bad plasma
I was thinking it was possible for the logic board to be your problem here, but 99.999% of the time, when it fails, it will cause colored lines.
There certainly is little loss if you want to try a logic, the part number is XXXXX and it runs about $15 on ebay, so you wont be out a ton to try it. But it has a very little chance of fixing your particular problem.
I am sorry Mark, I wish I had a simple fix, but there are only 4 things that cause horizontal lines, plasma panel, y buffer, y main, logic. You replaced two, and the 4th is not common to cause all black, normally just colored.
And the plasma panel, if you do not know, just the part would cost more than a new tv, so you would end up replacing it at that point.
Sorry again for the bad news, I enjoy helping people fix televisions much more than condemning them, but I am sorry to say in this case I cannot give you too much false hope that the logic will fix it.
Sorry again too for making you repeat yourself. 100% my mistake as I read your response for not catching that.
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