If it's only slight, it may indicate simply a small adjustment by an engineer.
If it's very severe ie. ) ( it's likely to be a fault in the E/W modulator circuits. Used to be very simple circuits, slightly changed with advent of widescreen TV. Usually, either the inexpensive E/W I.C. or an even less costly electrolytic capacitor will be the cause of these symptoms.
Don't run it with the fault. One customer of mine did this, eventually she called me out, it was a simple repair but the tube had a permanent image of the bowed sides left on it.
Shouldn't be too expensive to have repaired.
Cobweb, October 2004
