PURPOSE: To recognize a trouble part by the device itself when a trouble is generated, by providing a reading function of output signals at the output member of one means or plural means, and a means to decide the quality level of the output signals and the input signals responding to the output signals.

CONSTITUTION: Currents to be fed to focus lenses 1 and 3 are controlled by current control devices 10 and 12, the currents are read by current reading means 5 and 7, and the reading values are delivered to a reading value deciding means 14. A current to be fed to a deflecting coil 2 is controlled by a deflection control device 11. A current reading means 6 reads the current changing in the time series and delivers to a reading deciding means 15, while a high voltage reading means 4 reads the applied voltage and the radiating current. A central control means 15 delivers control signals responding to the observed conditions to the current control devices 10 and 12, the deflection control device 11, an image signal amplifier 13, and a high voltage generating device 9. The reading deciding means 15 compares the values delivered to control means and the reading values between the central control means 15, decides the quality level, delivers the results to the central control means 15, and displays on an image display means 18 and the like by the output signals from the means 15 to inform to the operator or the like.