[ Fascinating description of why use a TBC or the "
same" VCR for playback ]
This website caters mostly to PAL or EU style video, but also covers NTSC
http://www.ronaldsnoeck.com/vcr.htm
It goes into terrific detail describing Head Switching noise and all those things that make SP, LP, EP, SLP very different and how they effect sync.
It also covers what happens to sync when you copy a Tape.. there is really quite a bit known about that.
And why playback of a tape made on one VCR will encounter additional sync degradation when played back on a different brand of VCR.. hint.. there are no standards for drum size.. beyond each manufacturer.
And finally, what a TBC is good for.. why you (really really) want to use it and what it does for sync.
The illustrations are great.
If you like to get lost in video signals details you could spend an afternoon on the first page alone.