Can't get audio to work over HDMI

I cobbled this hackintosh from free used parts and (I call it trashintosh) and I can't get the audio over HDMI to work , the audio output on the motherboard works well however , i noticed it when I swapped the old HD4540 with an AFOX R5 230 because the latter is natively supported , the audio over HDMI doesn't work at all , the card works perfectly in Windows so it's not a hardware issue , I tried every kext and nothing worked .... I understand it's a very old hardware but I would appreciate it if you can help me

Specs :

• G31T-M9

• Intel Pentium E5300

• 4 Gigs DDR2 ram

• AFOX R5 230

• 80 gigs HDD

• OS X 10.10 (because motherboard doesn't support UEFI)