catsfan wrote:
s-video to the tv set; i have not used these jacks in a long time and
unclear if they were in use in the past


That may be your problem right there. Check the owners manual to be
sure but I don't think that unit will convert S-Video to Composite or
the other way around. In other words if you feed video to the RCA
inputs you must use the RCA outputs and if you use the S-Video inputs it
will only feed the S-Video outs.
Some units will do the conversion for you and others won't but I think
that's your problem.