Convergence is a feature found in rear-projection CRT (cathode ray tube) televisions that enables the user to realign the three individual picture tubes used to create the red, blue and green portions of the picture when the video displays a rainbow effect or other discoloration. This task is normally performed by using the remote control to access the feature within the menu settings, but with some TVs it is also possible to fix the convergence without the remote.
Check the front panel of your rear-projection television to see if it offers a button to automatically adjust the convergence. With some brands it may be labeled "Convergence" or "Auto Convergence," and with some Hitachi models it is known as "Magic Focus." If so, press this button and follow the on-screen prompts to begin the convergence process.
Press the "Menu" button on the front panel if your particular TV features such a button but does not offer a one-touch convergence button. Use the channel and/or volume keys to navigate through the on-screen menu options to see if your TV will allow you to access the "Setup" or "Picture" menu that contains the "Convergence" sub-menu.
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Enter the "Convergence" menu (when available through the front panel buttons) and follow the on-screen prompts for performing the manual convergence adjustment, which involves selecting a point on the screen and using the channel and volume keys to move the red and/or blue cursor at that point to align it with the green cursor, at which point it will then be shown as white.
Press the button designated by your particular TV to save the setting at that point on the screen, switch cursors and move to another point to adjust, which may be the "Menu" or "Mute" button. Press "Menu" when finished to exit the "Convergence" menu and then the main menu to see if the picture has improved.