Televisions can suffer from a number of display irregularities, but one common problem revolves around horizontal retrace lines that appear on the screen. Blue, green and red retrace lines can stretch across your television screen, ruining the quality of your display. Fortunately, you can operate on your TV and tweak the voltage and convergence boxes in order to eliminate the retrace lines and fix your TV. No previous experience with retrace line repairs is necessary.
Power down your TV and disconnect the power cord from the wall outlet.
Open the front panel of your TV. There will be screws on the front cover of your TV that must be removed with a Phillips screwdriver. The screw locations can vary significantly depending upon model. There will usually be two to four screws aligned around the speaker grille of the TV that must be removed.
Pull off the speaker grille of the TV. This will free up the rest of the front cover.
Loosen the front cover of your TV by prying around the edges of the cover and creating separation from the back of the TV. The cover will still be connected by a set of cables, so do not pull off the cover altogether.
Loosen the twist ties holding the cables in place, then set the cover off to the side of the set.
Find the wood panel or cover that is now visible directly behind the removed cover. This shields you from accessing the internal components. It will have to be removed. Take out the screws along the face of the panel with your Phillips screwdriver, then remove the panel.
Find the small black box behind the panel that has a number of cables running into it. This black box should be found near the front of all the visible components, just behind where the panel used to reside. This box controls the voltage and convergence adjustments for the TV.
Focus on the bottom of the black voltage/convergence box. There are three large screws here. These screws control the blue, green and red colours of your TV, from left to right, respectively. Retrace lines on your TV will differ by colour. If you are suffering from blue retrace lines, tighten the screw on the left with your Phillips screwdriver with a 1/8th rotation. Make this adjustment slowly and carefully. Green retrace lines can be fixed via the second screw, and red retrace lines via the final screw on the right.
Replace the wood panel, front cover and speaker grille of your TV.