Hello and welcome to JustAnswer.Do you still have the volume problem with the batteries out of the remote, if you use the buttons on the tv itself?
Ok,there is likely a problem (possibly a stuck button) on the tv's internal switchboard.
There is an easy way to test your remote to see if it is sending IR signals, I'll tell you how in a moment.
The method for determining if the switchboard is the problem requires opening the tv so you can disconnect the switchboard to see if the volume continues to go down after disconnecting the board.
To test your remote you can point it at a cell phone camera and press some buttons, if the remote is working ok then you will "see" it light up through the cell phone camera.
If this tv model has the IR remote sensor on the switchboard then you would have to turn the volume way up and disconnect the board to see if it stops going down. If this model has a separate board for the IR sensor then the remote should start working again after you disconnect the switchboard.
Let me know if you still have questions,Happy Holidays!
Ok,I believe this set has the "touch" buttons that light up when you press on that part of the frame. The first step is to clean the frame of the tv well before moving on to any other type of action. Try this first, if there is no relief from the problem then you would have to disconnect the switchboard, this set has a separate IR receiver so if the problem is the switchboard then the remote will begin to work once the switchboard is disconnected.
Clean the button area first, then move on to the next steps.
Ok, If they are not the "touch" buttons then cleaning has nothing to do with it. After you remove the back cover, you will need to disconnect the small plastic connection plug on the switchboard which is the board right behind the plastic buttons on the side. There is only one connector plug on this board and it just snaps in/out, hold the wires firmly and gently rock it while pulling out, take care not to use too much force so you don't break the circuit board.
You may want to try vigorously pressing each button repeatedly (usually with the set turned off) to see if that will temporarily solve the problem. This type of switch can go "bad" from NOT being used, so pressing them repeatedly sometimes has a positive effect. Give this a try before taking it apart.
If you don't get any response after vigorous, repeated pressing of each button, one at a time, then open it up and disconnect the switch board and plug in the AC and try the remote to operate the power, volume etc.