Your cable system is now HD and the JVC is not. So the no signal is correct as their is nothing for it to lock onto.
I'm missing a lot of detail here but it sounds like this unknown JVC recorder is from pre-HD days and as such is no longer useful.
After upgrading cable box to hd (couldn't receive all channels on standard cable box) I am able to view the picture from cable box but can't bring up menu for jvc recorder. Another cable configuration allows me to bring up the jvc menu but I have no picture from cable box only "no signal" flashing across tv screen.
TV has only one coaxial output (it was for the antenna. I used a rf modulator with the old cable box but same cable configuration doesn't work with new box. I have also called jvc and they were unable to help only telling me I had to purchase a new tv. Thank you

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