| 摘要 |
PURPOSE:To prevent deterioration in the quality of a display picture by providing a focus control circuit interlocked with the adjusting operation of a luminance adjuster, and keeping the thickness of an electron beam almost at a regulated level even when a luminance is stopped. CONSTITUTION:A color CRT (cathode ray tube) display device is equipped with a color CRT7, electron guns 3-5 of blue, green, and red, a CRT control circuit 6, and an adjustment circuit 12 consisting of twin variable resistors 21 and 22 interlocked with each other. The variable resistor 21 is used for a luminance adjustment, and the variable resistor 22 is connected in series to a focus adjuster 9, and is used for a focus adjustment. When the variable resistor 21 is operated to stop the luminance, the variable resistor 22 is interlocked with the above, and a voltage impressed on a focus electrode 11 is controlled so that each diameter of the electron guns is kept almost at the regulated level.
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