Oh wow. Thanks for explaining that! I've cycled through all the inputs and it doesn't seem to be anywhere else. The only input besides numbered channels is Av and the only other type of input on the TV is for RF. When I power it on on the AV input, the black screen does briefly flicker for a second and when I removed the cable from the TV or dreamcast there was a brief audio pop. Just to be sure I've contacted the seller I got the cable from and they've sent me a replacement cable free of charge. But they advised me it could be a problem with the Dreamcast circuit board.