I bought this 32 in Sanyo TV DS31580 at a Church sale w/ no remote-assured good picture. It has a great picture, but no sound. Do I need to use external speakers in the output jack?
After market remote works-no mute or low volume. Set for Stereo.
What can I say, It seemed like a good idea at the time.

Well first, I would get to the Sanyo web site and get the owner's manual download.

That way you would know whether you have a "Monitor" without a sound processor it it, very doubtful. Or someone has turned the TVs internal speakers off because they were handling the sound on an AVR unit.

You may want to pick up an universal remote and see if it knows your Ifr freq.