| 摘要 |
PURPOSE:To prevent surely ion baking on a fluorescent screen by closing a gate of an AND circuit so as to stop instantaneously the supply of a video signal to a cathode ray tube if a failure occurs in a deflection signal of the X, Y deflection system and a feedback signal. CONSTITUTION:If a failure occures in X, Y deflection system logical circuits 11, 12 or the like and a deflection signal and a feedback signal go to 0 level, an output signal of adders 23, 26 is lowered and an output signal of comparators 31, 32 changes from a high level to a low level. Then, the input condition of an AND circuit 33 is not satisfied and no trigger signal is applied to retrigerable MM34. Thus, the level changes from a high level to a low level for the retriggerable monostable multivibrator 34 after a set time constant is elapsed. Thus, the input condition to a circuit 35 is not established, the supply of a video signal fv to the catode ray tube is stopped and the ion baking on the fluorescent screen is prevented. |
