Fortunately, I accidentally discovered the cure for my previous problem(described below).
(I had been passing thru the VCR to by-pass the problem) But someone had accidentally
pushed a button on the TV (2nd from left) that had switched modes to HFC,or STD....
requiring me to use that button to get it back to CABLE....and EUREKA!...the switch must
have been dirty because the channel-locking problem was magically cured!
Another interesting (but unrelated) sound problem: most cable stations worked fine,
but a couple of them made the "SAP" lite come on, resulting in no sound. The panel buttons
could not disable "SAP", but the MTS" ? button on the remote did, which returned the sound.

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Need suggestions on Toshiba TV problem: (Model CF2750K, chassis # TAC-9011, Mf'd Nov 1991)
It works pretty well much of the time, but the Automatic Frequency Contol seems to
be "straining" to lock on to a channel after changing the channel. It usually takes a
second or two for it to "pull in" and lock. Sometimes it does not succeed, and seems to
lock in between two adjacent channels....sound from one, and weak video from the other.
My intuition is that there may be a single Capacitor-trimmer, or Potentiometer that
might "re-center" the "capture-window" and provide more certain "lock-in".
Can anyone suggest a specific adjustment, or an approximate location based on a similar
model? I do not have a schematic diagram. Thanks in advance!
(I was fortunate enough to get excellent advice recently which cured my Vertcal Linearity
problems!)