I think I didn't uninstall nvidia driver before install Rx 470 card
Drivers are loaded when windows starts. Windows can handle this alone - it will just hang on the first time and then load again without a driver.
On a 100% good card, You should see BIOS loading screen from Your mobo.
If everything is set and connected properly, it is like:
90% chance of card dmg
10% incompatibility problems
What You can do, is to install 750ti again, go to windows, download latest available motherboard BIOS and install it according to instructions given in manual/files description.
MAYBE it MIGHT help (doubt that). If not, i'd test this card in another pc to check if it even works.