Facing TV Problems? Ask a TV Technician.
Hi and welcome to JustAnswer, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.Initially, have you tried feeding the TV's L and R AUDIO IN jacks with a sound source? ...using a 3.5mm-to-RCA say from a mobile phone headphone jack?
How about a regular RCA-to-RCA cable?
If 1 end is connected to the TV jacks, touching the center pin only of the free end plug should produce a thump and/or humming sound from the Vizio speaker(s). This would test (at least the analog) audio circuit.
Yes please; both or 1 after the other. The idea is to use your touch to send a 60Hz hum.
Sorry; re-confirm; TV INPUT set to AV or COMPONENT? ...volume level all the way up?
Then it would be an internal hardware issue.
Are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter (and even perhaps a soldering iron)?
Great on the DIY!
The prescribed approach is to run tests; i.e. voltage measurements, compare with expected readings from the schematics/Service Manual, determine most likely suspect component, test out-of-circuit, replace, test again.
Or take a blind swing and replace the whole board.