To answer my own question, you don't. You have to buy a replacement main board with both the correct main board part number and also the correct TXN which is TXN/A1JQVB in my case (this is printed on a label stuck to the main board). I expect this relates to what firmware is loaded on the board...
It seems the main board has come out of a 55" version (TX-55CX680B) and mine is a 50" (TX-50CX680B). Although the board is the same part I've come to the conclusion the software on it will be different. So, question is how to I install the correct software onto the main board for my 50"?
Hello all,
Our Panasonic TV (TX-50CX680B) wouldn't power on (after a lightning strike took out our phone line, router and TV via the ethernet cable) I diagnosed that the main board had blown so got one online and replaced it with the same model no. (TNPH1120 2A). TV now powers up and functions...