I have successfully hooked up my cable box to my receiver, with my television receiving a composite video-only input. I attempted to hook up my DVD player to the receiver via a digital optical cable, but it didn't work, first giving me audio only, then nothing. I plugged in a composite A/V cable instead, which works. Although it won't make much difference for my old television I would strongly prefer to have digital sound.
So...what's going on? Anything I should check before I put out for another optical cable? (I can't think of where I went wrong. You plug one end in the optical output of the DVD player and the other in the receiver where it says "Digital Optical Input - DVD." Not exactly brain surgery.)