Is to get the service manual to see what it says to measure and replace next. Without that and the usual voltage readings we are guessing. Lost audio could be speakers unplugged or other simple issue.
Try latest firmware and a factory reset. Also, with so many audio choices today, why not button it up and use a sound bar?
I have seen similar problems on this forum but I am reposting for better clues. My LG 3d led tv screen went out and no volume. I have already replaced the power board thinking it would fix it. I am at an end. any help

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