pc sound not working

Hi, first time posting here, My motherboard(b450 gaming plus max)'s sound isn't playing , no matter what I do it just doesn't play, this happened after I replaced my motherboard. So I had the b450 it was working then when I switched it cause I found some pins fell off to the same model b450 it...

Just purchased the lg 55" UHD 4K 55UH6030 and i am trying to hook it into my existing sound setup. On my old tv i used two rca cables audio out to the aux inputs on my Pioneer SX-1000TW receiver. Problem is the new lg tv has only optical out or h/p out. I tried buying an optical to rca...