VHS verticle jitter on some VCR's but not others

[n6nfg]

I have a few VHS tapes that have been played a lot and have
become unwatchable on some VCR's in my house but not on
others. The symptom is what appears to be a verticle jitter that
appears to be only a few scan lines high and occurs for the entire
hight of the image, like the entire frame is moving up/down at
a 60 (or 30?) times per second rate (NTSC), It occurs on either
a paused frame, or in real time just playing normally. There is no
obvious tearing of the top or bottom of the picture, and no noise
distortion anywhere either.

Has anyone seen this?? Most tracking failures I have witnessed
have had either the top/bottom edges tearing, or have noise/snow
evident in parts of the screen. Mine is a nicely formatted picture
that just vibrates up/down!

Would a external Time Base Corrector allow me to capture these
types of tapes to save off the content before it gets any worse?

-n6nfg

[LanEvo7]

I have seen this on my VCR. Sometimes its just a crappy VCR. I had a VCR that wouldn't even play some tapes, other it would have vertical jitters. I switched to a Sony and all the problems were gone.