Hi Edwin Robinson,
First of all thank you for contacting Fixya.com regarding your TV problem.
You didn't mentioned if the symptoms remain the same in all inputs, this is to isolate the AV board from fault. If you are using HDMI connection, I would advice you to try the other inputs like input 1-3 at the rear panel and the Audio/Video input at the side panel using the RCA cables. If there's no sound after trying other inputs, then this is an indication that the fault is in the audio circuitry inside the TV.
The DIY steps that I would advice you is to check the resistance of the internal speakers using the multimeter set in resistance measurement. Good speakers will read between 6-8 ohms (for 8 ohms impedance) and you can hear a crackling sound upon testing.How to test speakers
RCA Cable Connector
If the speakers are in good condition then the fault either the supply voltage line of the audio circuitry from the power supply board, the audio processor on the main board or the sound output circuitry. This require technical skills because series of test are going to perform to isolate where the fault came from.
You can still watch your favorite channel and movies to your TV while the sound is playing through your home theater system or amplifier. Just hooked up the video to your TV terminal jack and the sound/audio to your home theater system or amplifier to bypass the sound from your TV.
Please let me know if you need further assistance.
Have a nice day and take care!