استخدام المحول في دارات التغذية وميزاته .. كتاب التلفزيون الملون والعادي

3-12 The use of the transformer in the supply circuits and its advantages:

The use of the transformer in the supply circuits of monochrome or color television seems more expensive than other methods, but it includes the following advantages:

1- It secures the isolation of the supply +B and the heating filaments in the valves from the AC source, thus ensuring the protection of the person who may touch the points of the metal body by means of independent coils in the chassis feed transformer from electrocution.


2- The continuous voltage B is generated with better output and regulation, which extends the life of the device.

3 - Ensures that the filaments of the valves and screen are fed with high DC bias voltages.

4- When the transformer has a middle point in the secondary, it is sufficient to connect two diodes only to make a full-wave rectification circuit instead of four diodes (12-4).

E - If some of the fuse fuses are parallel, the current of each of them may differ from the other.

6 - The device can be easily set to the appropriate voltage through the primary multi-feed transformer (110 - 200 - 220 - 240 volts).

7- Some high-quality colored devices contain a voltage-stabilizing transformer so that the output voltage is not affected by the input voltage.

The use of the transformer in valve devices:
In some of these devices, the transformer secures the continuous positive voltage +B and feeds the screen valve heater - while the filaments of other valves are connected in series and fed with alternating current AC, and since the bias of the screen valve and the damper valve or damper reaches a large value of 100 to 200 F continuously Therefore, different feeding must be provided for each of the heater and the cathode, in order to avoid the occurrence of a short circuit between them - Figure (5-12) shows the feeding circuit of the device with the feeding of the filaments, and the bias voltage of the filament windings reaches approximately two-thirds of the voltage (B). It is noted that one of the two AC lines is connected to the ground of the device. The end of the filament line is also grounded, and in the previous diagrams, the feeding of the screen valve and the damper valve is independent of the rest of the valves in the device.

Feeding circuits without a transformer:

We use it in TV sets, including the circuit shown in Figure (6-12), which is a half-wave rectifier circuit - it has a filter capacitor at the entrance (it is for a 14-inch TV, and the fuse fuses are connected in series with a resistance of 38 ohms in AC current to reduce the voltage of the wicks, while the intensity Its current is (450) milliamps, and the reduced voltage is 38 x 45, 0 = 17 volts