Soft-Flash Picture Tubes

Between the gun electrodes of picture tubes, high electric field strengths are present. In a typical color picture tube there is a voltage difference of some 20 kV across a gap of about 1 mm, between the focus electrode and the anode of the gun. Although the utmost precautions are taken in the design and manufacture of the tube, there is always a chance that a flashover will eventually occur. When it does, the discharge current rapidly reaches a very high value, inducing voltages throughout the receiver chassis which may destroy semiconductors. Even with the most careful circuit layout, complete protection is difficult to ensure.