Do you get any signal out when feeding a 75 ohm load?.
My experience over the years was that it worked fine as the computer booted up, displaying the DOS commands, but as soon as Windows fired up all outoput from the AV outputs ceased.
I spent months on forums and emailing technical support, but never managed to get one to work.
What are you actually wanting to do?, I presume you know that the quality via a TV will be absolutely dreadful, OK for watching poor quality DVD's, but useless as a monitor.