First, try some other audio device in the unit to see if it plays stereo. If not, the optical port may be dirty and require cleaning. If the other audio device plays, check to make sure the plug on the earbuds is clean. If the earbuds still don't work, you might have a broken wire — but if you get to the point where you're splicing in new wires, I would be more inclined to buy another set. I'm seeing these, unused, on kijiji for $5.