Just finished installing Linux Mint 19.2 64-bit into an AMD A4 3.7 GHz rig. Everything works except sound output. The icon for speaker volume at the right lower corner is there, I can change volume output level via the slider there. But there is no sound from my speaker plugged into the rear or front sound jack. I look into the sound settings, the sound output is directed to Dummy Speaker icon, and there is no other choice displayed. Yet, if I switch hard disks to boot into Windows, the sound is there, loud and clear. What's going on, and how do I fix this?