Hope someone has some good advice for me. I bought the Magnavox H2160MW9 HDD & DVD recorder to perform timer recordings. I hooked it up to my Comcast cable box and tried to record a show. When I went to playback the recording the picture was fine but there was no sound. If I record while I'm watching tv I get sound. This is the second setup i've had with the same result (i've tried a different cable box and a different recorder)any thoughts on the problem?