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Hello. My name is Michael. I can help you with your question.
The most common problem on this model, by far, are the capacitors on the power supply. But since you have already checked that and ruled it out, the first thing I am going to do here is upload the service manual to my OneDrive so you can download a copy. Here is the link:
There are two separate control inputs on P201. There is the On/Off input which you have overridden, but the last pin on the other end of P201 is '3.4V ON', so the 0V doesn't surprise me. I think you have a bad main board, yes.
Sorry. the system didn't alert me to your reply it seems.
It is true that UK/AZ/US boards are often the same. You should try to get an exact match for the number on the board. Occaisionally, one revision of the board is not compatible with other revisions of the board because other electronics sometimes change when they make a revision. But if you can't find the original board, usually the site will be smart enough to tell you whether it has to be the exact number or not. Or if it is compatible with more than one.
OK, if the numbers match, then you are all set. That will be a fun Christmas Eve!
If you wouldn't mind - if you rate my service - it will stop the question from closing or going back into the open question pool - so that when you reply, I will be notified.
Since the symptoms changed, I would say that the board is defective. I would ask them to send you a board that they have tested and they are certain works. Audio is processed by the main board, so if that is having a problem now as well, then it would make sense that the main board is the problem.
Thanks... you didn't interrupt anything! I was stuffed by the time I responded.
Let me know how you make out.
That all sounds correct. Yes. It looks like you are extremely close. If everything works now except for the backlight, then it's just the inverter boards.
It's not uncommon to have to go through more than one replacement board when they are "refurbished" (used). Unfortunately, many of them are not tested before they are sent out. And often, when one board goes, more than one goes, so not all boards pulled from a set that are assumed to be working actually are.
Are the new inverter boards new or used?
So... it is possible that there is something else causing these boards to go bad. The buzzing in the inverter to some extent is normal, but loud buzzing may mean that they were the wrong boards or getting the wrong voltage.
OK. Should be working. But as I said about used parts, you never know.