| 摘要 |
PROBLEM TO BE SOLVED: To prevent production of stray emission with an inexpensive circuit means by forcibly decreasing a 2nd grid voltage in the case of power-off and video frequency switching so as to suppress emission of stray electrons from a foreign material such as a cathode material deposited on a 1st grid or the like. SOLUTION: When a cathode ray tube is in operation, a flyback transformer 31 applies a voltage VG2 of about 300-700 V to a 2nd grid. In the case of power- off and video frequency switching, a command signal pulse voltage 26 reaches 0 V, a base level of a transistor(TR) 1 is decreased via a resistor R1 and the TR 1 is turned off. TRs 2, 3 are both turned on attended therewith and a current from the flyback transformer 31 flows to GND via resistors R6, R7, then a 2nd grid voltage is decreased by a voltage division ratio by the resistors R6, R7. In the case of video frequency switching, since the command signal pulse voltage restores to +5 V in 1 to 2 sec, the 2nd grid voltage is restored.
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