Hello, Welcome to Fixya
If the mute is ok, you want to check if your have a cable or sat box that the mute on those are ok as well, if so then your looking at a internal issue with the TV that would involve repair.
1. unplug the tv wait 10-15 seconds
then plug it back into the wall outlet.
2. unplug any cable boxes or sat boxes that might be causing
If you still are having issues you might want to check it into a local repair shop near you, but take this advice for what its worth you might wind up paying more for the repair then the purchase of a nice flat panel.
Make sure if you do take it into a shop that there registered with the BBB and do not have complaints registered as those shops could end you paying more money.
Thanks for making Fixya
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Rulds2008 Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/edwy_1a56970cf1ea4620