Mac tuns on but no chime/ no headphone sound

Hello everyone! I hope someone can’t help with this weird situation. I have a 820-2879-b board that turns on and does not chime or have any audio through the headphones. So to be specific the unit turns on and loads to desktop and works ok except the chime is not heard and the sound for the internal speakers only has treble no woofer from the left speaker only. Also, when I plug the headset in the sound goes off the internal speaker and nothing comes out of the headset! What I’ve tried is: reset pram and SMC but to no avail! Can someone give me another route, I’ve exhausted any ideas! Thanks!