Hmm. That’s a tough one. Since it transmits and receives we can probably rule out a faulty audio chip. The only thing i can think of is that the external speaker plug is bad. If it’s stuck in the “inserted” position it would disable audio to the internal speaker even if nothing is plugged in to it. If it’s broken even an external speaker wont work. It could also have a cold solder joint as those Galaxy’s are pretty old now. Ranger's and Galaxy’s never really did have good solder joints to begin with. I’d start with getting some
Deoxit and clean all the pots good (volume/sq/mic/rf/gain/etc). If that doesn't work, pull the top cover off and look at the solder connections for the ext. speaker jack for cracks/loose connection. Short of that, i’m out of ideas. A trip to a local tech might be in order to diagnose and repair it.