| 摘要 |
A cut-off adjusting apparatus in which a signal source for detecting cathode current is not required, the cost can be reduced, the cathode current can be detected with high precision, and the correction corresponding to time-variation can be performed with high precision. Includes a controller in which when an enforced adjusting mode is set, during a vertical period a control signal is output to a video amplifier to output such a signal that no video signal is contained in the output and the pedestal level is the black level irrespective of the input video signal, and wherein an averaged cathode current at this time is detected. Subsequently, a control signal is output to the video amplifier to output such a signal that the brightness level is set to gray, an averaged cathode current at this time is detected, the differential value therebetween is determined, the measurement value thereof and an initial set value are compared with each other, and a control signal is output to a third terminal of the cut-off control amplifier so that the measurement value is equal to the initial set value.
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