My Vizio is older model M320NV,
On mine use menu button
Goto settings
Tuner
Choose Cable
Then do a channel scan
I Believe there was a change in FCC regulations a few years ago, regarding tuners and encrypted cable, and wether or not that capability had to be included, you have TV's with different model numbers, it's possible those that won't receive/ display the cable signal can not decrypt it, the software in the tuner is not programed for it, or the tuner lacks the chip that provides the reception for the frequency the cable signal is on
Click For Full-Size Image.
Both models of your TVs list "Clear QAM" for the tuner, neither can decrypt encoded cable , according to the manuals and the listed capabilities, he tuners have the same ability,
But clearly they do not, how does the picture compare if connected to your RV antenna, maybe the new model has a weaker tuner that needs a stronger signal from the cable, (yes I know Digital is usually on or frozen , no such thing as a snowy image) (but it will jitter, jump and freeze, new image then freeze when there is variation in signal strength) , I wonder if a TV signal amplifier between cable and the TV would help,
There was time before I moved to Calif, when I worked as tech for the local cable company back in Hoosier Land,
Long long time before DTV, but I do remember a few things I learned back then
I can explain it to you.
But I Can Not understand it for you !
....
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1997 F53 Bounder 36s