Color CRT drive apparatus and CRT display including a brightness adjustment

A drive apparatus for a color picture tube, comprising:

• a video output circuit which receives video signals, amplifies said video signals and outputs the amplified video signals;
• a picture tube drive circuit which receives the amplified video signals from said video output circuit for driving the color picture tube based on said video signals, said picture tube drive circuit having means for detecting a beam current corresponding to the brightness of each color flowing through said picture tube;
• a picture tube connected with said picture tube drive circuit for displaying the video signals;
• a white balance control circuit into which a detection value of a beam current detected by said picture tube drive circuit is inputted and for outputting level compensation video signals, for adjusting the white balance of the video image displayed on said picture tube, to said picture tube drive circuit;
• and
• a brightness adjustment circuit including an adding circuit, a comparator, a switch, and a brightness control source, said adding circuit being provided in a line delivering said video signal, said video signal being inputted to one input of said adding circuit, an output of said adding circuit being inputted to an input of said picture tube drive circuit, an output of said comparator being connected to another input of said adding circuit, one input of said comparator being connected to the output of said adding circuit, said brightness control signal source and said white balance control circuit being connected to another input of said comparator via said switch, and said switch when switched to said white balance control circuit side inputting a white balance adjustment reference signal to said picture tube drive circuit during white balance adjustment.