You indicate that you are plugging the TV output connectors to the PHONO input on your JVC receiver. I would suggest moving that connection to the AUX input to insure that you are not overloading the PHONO input. The PHONO input on most receivers expects a turntable with a MAG cartridge which has a very low output. Some receivers have AUX1 and AUX2 inputs. Also, make sure that the audio out for your TV is enabled.

Yikes! As Mike pointed out, you don't want to use the phono input as it is meant for a very low level magnetic phono cartridge signal that is much lower than the "line level" output from CD and tape players. The headphone output level is also higher than the normal "line level" but it can work. You do need to use a line level input however.

Since you don't have CD or tuner output either, start there. You didn't mention the model of the receiver (please do so if you can) but make sure that things such as "A-B" speaker selectors are in the "A" only position and you are connected to the "A" speaker outputs. Also make sure you do not have a "tape monitor" switch in the on position.