| 摘要 |
PURPOSE: To provide a focus circuit having a simple and inexpensive constitution and which is capable of obtaining a focus voltage in which dynamic focus voltages arc superposed. CONSTITUTION: The one side of terminals of a volume 16 is connected to the diode 4c of a flyback transformer 1 and the other side of the terminals is grounded. The moving piece of the volume is connected to a focus terminal 8f via a resistor 17 to supply the DC component of a focus voltage FV from the moving piece. A voltage generating part 19 is connected to the terminal 8f via capacitor 18 and a voltage DF2 having a desired AC component of the focus voltage FV is supplied to the 8f from the voltage generating part 19. A desired voltage FV in which the AC component from the voltage generating part 19 and the DC component from the moving piece arc superposed is supplied to the terminal 8f. A resultant resistance value RVR1 (the parallel resistance between 16a and 16b) and the resistance value R17 of the resistor 17 and the capacitance C of the capacitor 18 are set so as to satisfy (RVR1+R17)×C 18>(1/100)sec.
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