A friend has phoned to say that he has picture but no sound on Sky. He has the basic Sky box - not HD . He has Sky link to bedroom and has no sound on either set when on Sky. Sound is OK on both sets when tuned to terrestial channels. He has not paid for insurance with Sky and so is not covered for repair/replace. I have a spare Sky HD+ box, would this work? I know that there are two inputs with HD and only one with basic, but would this be a problem?