TV GOES ON AND OFF BY ITSELF AND SOUND GOES UP AND DOWN BY ITSELF

Turn up the sound then take battery out the remote if it still goes down it might be dust in the volume button on tv

The problem is with the ckt that controls the manual keys on the TV.Disconnect it and the rest should work with your remote.

Audio control section circuit at the main board faulty. Contact any service technician. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/

unfortunately the coby company has gone out of business probably because they have produced an inferior product that has had many problems, many people are posting problems with these sets. it is better you just purchase a different brand of tv and leave this heartache causing product behind.

There is no sound card separately. The audio output circuit is a part of the main board itself. Check its speaker first.

If you have tried using different input devices, looked for loose contacts
in power outlet, RC Jack, cable and connectors, the TV might need service. Also look for any jammed buttons on remote.

sounds like a bad color wheel

I have this same TV and had a similar problem. This may or may not be the same case with yours. The button panel on the front of your TV may be having connection problems. Mine would come on and off by itself. I took the front panel off and cleaned the connection on the button board with a q-tip and a little dab of alcohol. This cleared up the problem of it turning itself on and off.

I had a similar problem where my 61" Samsung DLP was turning itself off very frequently I had resolved to try replacing the bulb. I called a local TV repair place to see if they had my buld in stock. The guy I spoke to actually told me how to fix my problem! There is a little blue switch behind the bulb access door. The inside of the door has a little piece that presses the switch down. The switch is supposed to work correctly weather the switch is in the up or down position but samsung forgot to take expansion from heat into account. If the switch is held in the upper position by the door and the plastic expands to a certain point, it triggers the set to shut off. This does not occur of the switch is held in the lower position. What you need to do is take the access door off and put it back on by sliding it into position from above. That will hold the switch in the down position, eliminating the problem. My set has not **** itself off ever since.