I am an electronics technician who use to repair Samsung TVs at PTS/Moduslink (knowledgable).
I am trying to connect my piano keyboard to my home theater sound system. It works if I plug into the aux input at the surround sound decoder, but that is 35 feet further away from my piano than my Samsung UN65RU7300F TV. I tried to plug the piano into the audio jacks of the Component input on the TV but there was no source choice for component/composite, so I could imagine that the electronics would require an RS-180a signal before it would provide the Composite input as a source choice. I looked around to find something that outputs this video signal, finally I found an old RF convertor and plugged its video signal in. There still was no choice for Composite so I thought perhaps the convertor was broken. I looked inside the convertor and it was looking OK, so I try this again. This time I plugged in both the video signal AND the audio jacks from the piano, and now there is a choice for AV input as a source, but upon selecting it the audio is not passed through the TV.
There are two issues here.
First I believe the component/composite input jacks on the TV have small micro-switches on them and it is these switches that enable the AV input as a choice to show in the Source list. This is how the TV 'knows' the input is present and whether it is composite or component. Is that right?
Second I believe that the RF convertor is not actually sending any video because I don't have an antenna connected to it. It is not mine I just found it at work, so I don't know how it is supposed to work (there must be a remote and I don't have it). But as you can see I don't care about showing any video I just want the audio signal from my piano to go to the Home Theater system and come out of the speakers without running another long wire across my living room. The connection from the TV to the Home Theater system is an optical cable (of course).
So if I use a long wire I can verify the piano works, the cable from the piano to the TV works, and the AV input is selected on the TV, but the piano sound does not go through the TV to the speakers.
I believe that in order to get this to work, I would have to provide an RS-180a video signal to the Composite input. I believe that the Samsung TV will not pass just the audio through itself, that the internal "logic" of the design is to mute the audio unless there is a meaningful video signal. Is that right?