NotTaR of Television Sets : Horizontal lock lost                    
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Horizontal lock lost

A TV which loses horizontal lock when changing channels, momentarily losing the signal, or switching inputs may have a horizontal oscillator that is way out of adjustment or has drifted in frequency due to aging components.

Note that the characteristics of this are distinctly different than for total loss of sync. In the latter case, the picture will drift sideways and/or up and down while with an off frequency oscillator, the torn up picture will try at least to remain stationary.

This could be a capacitor or other similar part. Or, the oscillator frequency may just need to be tweaked (particularly with older sets). There may be an internal horizontal frequency adjustment - either a pot or a coil - which may need a slight tweak. If a coil, use a plastic alignment tool, not metal to avoid cracking the fragile core.

A schematic will be useful to locate the adjustment if any or to identify possible defective parts. Try a large public library for the Sams' Photofact for this set.