Curved blue lines on screen.
You have a completely different problem. The screen voltage for the blue picture tube is slightly too high on your set. This will put fine lines in the background of the picture, called retrace lines. This is very common and easy to correct. Remove the front speaker cover and the access panel behind it. Look inside and you will see a black box with six controls, each control having a little white glue on it. This is the Focus/Screen block. Three controls are labeled Focus and three are labeled Screen. The screen control in the center is for green but I am not sure if the screen control on the left or right is for blue for your model. With the TV on, set it to VIDEO 1 but do not connect anything to the VIDEO 1 jacks. This will produce a pure dark picture, showing any faint lines in the background. Choose one of the screen controls and increase (turn clockwise) it slightly. If the blue lines do not get brighter it means you are turning the red screen control, so put it back where it was and choose the other screen control. When you find the blue screen control, decrease (turn counter-clockwise) it until just when the blue lines are gone. If you want you can check that the red and green screen controls are set to just below the point where their faint lines are visible. When done, replace the panels and your picture will be back to perfect.