not connecting to external display

Hi, so, i recently aquired a macbook pro with backlight issues. it did connect at that time to an external display though. however, i'm trying to get it to connect using mini displayport to hdmi but sadly my tv doesn't picks it up. I'm afraid it's graphical chip issues but i don't want to jump to conclusions. It does not has a OS installed, just a blank 500GB HDD. how do i get it to connect and show up on the external monitor from boot.