I have a NVIDA 555M. 5 months ago i installed Mavericks and the Sound, Graphics and Network works very good, the problem now its on Yosemite Zone, mi graphic card not works, and my Audio neither.
Why, on Mavericks Distro all worked fine.
I also install a backup kext from Mavericks, afeter that my Screen no signal.
At finished a clean instalation my screen no signal. I repared this with this post https://www.hackintoshzone.com/hackintosh/articles/how-to/fix-grey-screen-black-screen-mac-os-x-installation-hackintosh/, but Next i install my backup kexts, and the problem returns.
The Audio its a little problem but the graphics its a big problem
Intel Core-i5 Second generation @3.00 Ghz and 4 nucleus
NVIDIA GT-555 M
My model computer its a Lenovo B520