Hello... Can you borrow/use another Video card? Can you use/borrow a standard computer monitor?
What are your TV/brand/Model specs? Have you ever Hooked a computer to your TV before this? Have you got the TV on the right HDMI input and settings for that input?
This sounds similar... http://www.tomshardware.com/forum/312477-30-asrock-extreme-problem
If the Above ideas don't help you... re-post with your Motherboard and CPU info, also search the forum for people that had similar problems solved, for more experienced help in those areas... Best of Luck.