karn (12/09/82)
Problems in viewing prerecorded video tapes are often due to a "feature" known as "copyguard". This is an attempt to prevent unauthorized copying. It involves modifying vertical sync in such a manner that the servo circuits in a recorder cannot lock to it, but that MOST TV set sync circuits can. Some sets may be more sensitive to this, however; a typical symptom is a touchier-than-usual vertical hold adjustment. At most hamfests, one can find copyguard defeater circuit kits which reconstruct the proper vertical sync pulses. This makes the tape easier to view, and not incidentally, makes copying possible. (But you wouldn't do that, now would you? :-) Phil Karn