PURPOSE: To eliminate an unpleasant picture output state which is produced when a power supply is applied by allowing the supply of image signals after the electron discharging capacity of the cathode of a picture tube is stabilized during application of the power supply of a color TV receiver containing an automatic white color controller.

CONSTITUTION: A reference signal inserting circuit 100 inserts a reference signal via a synthesizing circuit 13 in a blanking period of a video signal. A sampling circuit 33 and a comparator 35 detect the cathode current of a picture tube in said inserting period of the reference signal and control a level correcting circuit 18 based on the error voltage to the reference voltage 36. Thus the white color temperature is automatically corrected to the standard level. A transmission preventing circuit 200 monitors the output level of the comparator 35 and supplies a preventing signal to a signal control circuit 57 when the cathode temperature is lowered during application of the power supply. Thus the video output to be supplied to a matrix circuit 12 from the picture tube is cut off. Then an allowance signal is delivered to restart the supply of video signals when the cathode electron discharging capacity is stabilized.