WIFI not connecting, speaker icon greyed out

i recently upgraded to Yosemite and started experiencing WIFI issues. after getting fed up with the poor wifi in Yosemite i wiped my hard drive and reinstalled Mavericks hoping to resolve the problem, however now my wifi will not connect in Mavericks either. i also tried booting Lion from an external drive and the problem remains. since then i have tried a PRAM and SMC reset and also tried repairing permissions however nothing has helped the issue. in fact since the SMC reset my speaker icon in the menu bar is now greyed out and wont allow to adjust volume. i have also run an Apple Hardware Test but everything is checking out ok. starting to wonder if my logic board might be fried, any ideas?

Thanks,

Josh