In our magazine and other electronic literature published many descriptions of different devices to protect the picture tube from premature failure is when you turn on the TV. Another interesting variant of this device using the rectifier discussed in published material here.
To protect the filament of the tube when you turn on the TV and components gradual heating of the cathode (cathode) of the tube is proposed contactless device, scheme of which is shown in the figure.
It is a variant of the node constraints and delays, for which limit the filament voltage when you turn delay the filing of its full value serves as a vacuum tube diode (rectifier) VL1. The transformer T1 accords the resistance of the filament circuits of the tube and diode VL1.
The primary winding of the transformer included in the filament circuit of the tube. To secondary boosting winding connected to the rectifier bridge VD1, loaded at the rectifier VL1 and thereby providing a gated diode VL1 some time after power output voltage 220...240 V. It is used for closing electronic spotlight (spotlight) of the tube during warmup it the cathode (cathodes).
At the moment the TV is switched on, the voltage on the filament of the picture tube from falling in inductance of the primary winding of the transformer T1 is reduced about to 3.25 V At a current of about 0.4 A. for 18 with the result gradual heating of the cathode bulb VL1 appears and increases to 30 mA current through it. The rectifier shunt across the diode bridge on the secondary side the transformer T1. Simultaneously, the voltage of the filament of the tube grows to 6.3 In at a current of 0,8...0,9 A. the voltage at the output of the diode bridge VD1 smoothly drops to 5 In over 25 due to the shunting effect of the tube diode VL1.
The fall time blanking the kinescope voltage-dependent time constant circuit modulators of the tube, i.e. mainly on the capacitance of the capacitor C1. Diode VD2 plays the role of the separation between the time-setting chain tension and modulator of the kinescope.
As a matching device used output transformer sound from TV Raduga-703". To ensure automatic regulation it is necessary to raise the voltage on the filament winding of the power transformer to values of 8.4, additional winding the coil on top of one of the coils of the power transformer. This winding, containing five turns of PEV-1 with a diameter of 0.55 mm, connected in series and in-phase main.
Author: A. Zhadobin, Moscow