There are a wide variety of causes for a TV that will not display a stable or
properly configured picture. Among the symptoms are:
Lack of sync horizontal - drifts smoothly horizontally. Depending on the
difference between the video horizontal rate and the free-run frequency of
the horizontal oscillator, the picture may be torn left or right (as shown
in Symptoms of Some Common Deflection Problems
or have multiple images superimposed horizontally. The situation where the
picture is neatly split horizontally (which is what you might expect) is a
special case where the frequencies are virtually the same. The key symptom
common to all these is that there IS vertical lock (no blanking bar visible)
AND there is no evidence that the deflection is even attempting to lock
horizontally.
This may mean that the horizontal sync signal is missing due to a sync
separator problem or that there is some other fault in the sync processing
circuitry.
Incorrect lock horizontal - a more-or-less stable torn picture. This means
that the sync signal is reaching the deflection system but that it is having
problem locking to it. The horizontal oscillator free-run frequency may be
too far from what it is supposed to be (15,734 or 15,625 for NTSC and PAL,
respectively).
Lack of sync vertical - rolls smoothly vertically. This may mean
that the vertical sync signal is missing or the deflection system is
ignoring it.
Lock not stable vertical - jumps or vibrates vertically. This may be a
fault in the vertical sync circuitry.
Multiple or repeated images horizontally or vertically. Problems in sync
processing circuitry.
Additional comments on some of these problems follow in the next few
sections.
