iMac does not recognize external monitor using Mini Display Port to HDMI

Hello,

I have been trying to get an external monitor (HDTV) set up for use with my iMac using a Mini Display Port to HDMI cable I just got. However, when I connect it to my iMac's mini display port, the imac's screen goes black for about a second, then returns, but it does not detect the external display. The other display is just showing a "no signal" message on the screen.

I have restarted, reset PRAM, connected and disconnected the cable several times, tried changing the resolution on the imac, plugged in/out the other display, and clicked the "detect displays" button using the option key in display preferences, but nothing has worked.

I am using an early 2009 iMac running Mavericks.

I've been using the AirParrot app, but it's horrible for video and a little slow.

Can anyone please help sort the issue here? I feel like ive exhausted everything that I know to do.

Thanks.