Does no focus mean bad flyback?

dyno

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The focus knob on my flyback doesn't do a thing when turned, the flyback is new. The socket on the neckboard has been changed and still the focus knob does nothing. If the focus knob does nothing when turned does that usually mean a bad flyback. Sometimes the picture on the screen will drift out of focus but I can get it to come back by turning the screen knob on the flyback.
 
Not usually... usually it means a bad connection somewhere, or a bad tube. The knob on the flyback is just a potentiometer, if it was bad you'd still get some sort of change when you turned it, it'd just drift and change on it's own.

The screen knob is just a way to adjust the screen voltage, as it goes up and down it changes the focus, that's normal. Look on the schematics and see if the focus voltage runs through and resistors or anything near the flyback since you've already swapped the neckboard.
 
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