You can check it by reducing the value of the resistor, connected to ground at one end of the deflection yolks' vertical scan out windings. Usually, this resistor will vary a value of 1.2 Ohms to 2.2 Ohms. But, if you reduce this value too much, to say at about 0.15 Ohms or so, there is a possibility of damaging the vertical scan output IC.
So, do this very carefully. It is a trial and error process.
Check it with gradual reducing this value of this resistor; by 0.25 Ohms at a time. Wish you success. I hereby advice you, assuming that the horizontal width of the picture is OK.
If you wish to get some details; check the site linked here. Viewing it in "
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Magazine" will make surf easy Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/
