This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
The fix may be fairly easy. Try plugging Stereo headphones into the Sound Output jack on the back of the GS. Whatever you plug in (headphones, a connection to an amplifier, etc.) must have a Stereo plug. If you get sound through the headphones but no sound when the headphones are unplugged, it means that your jack is, probably, messed up. There's a leaf switch which is part of the jack which is supposed to close and connect-up your internal speaker when nothing is plugged in. If this switch's contacts become dirty or the leaf loses its springiness, the switch fails to close. The easiest long-term fix is to either A. solder a jumper which keeps the switch closed whether or not anything is plugged in or B. plug in an external speaker (using a Stereo plug). Another, fairly rare, cause of Sound loss is that the internal Speaker "+" lead has been pressed against a pointy Ground circuit point on the motherboard. This sometimes happens when the small front panel and/or the motherboard has been removed and replaced without making sure the Speaker lead is routed correctly. If neither of the above fits your Soundlessness problem, describe your system and post the question to Csa2. ----------------------------