uninstall-reinstall

hi guy's back again i partitioned my hard drive and installed my snow leopard video port would not work still so i just up graded diectly to yosemite and the computer is faster than ever but still no video out can it be blown up and if so is it easy to replace i had all my stuff backed up in iCloud and on a 128g usb drive so was able to re-install

all my things so it is printing and every thing else works fine except the video port .......

not sure were to go from here may be my tech