Duo sound issue

From George Plamantouras <xxxxxx@mindspring.com>
Date
i have this beautiful pc engine duo in a box sitting around.  as i have 
a north american duo and a duo rx, it's become obvious that i no longer 
need this baby.  i plugged it in to test it out to find a serious 
problem: no sound.  when i popped the headphones in, i could barely 
make something out but it seems nothing goes out to the tv.  everything 
else is fine.  i have read about this issue before though had never had 
to deal with it until now.  i also seem to remember that it is a fairly 
easy thing to remedy.  any suggestions?   yes, before you ask, i tried 
using different cables only to get the same result. this has to be 
something internal. right?