أعطال دارات الانحراف الأفقي .. كتاب التلفزيون الملون والعادي

17-19 Faults of the horizontal deflection circuits:

Regardless of the type of circuits used in the stages of horizontal deviation.

Most of the faults are manifested in the following parts:

The elements of the amplifier.

2- Power diodes or output transistors.

3- Thyristors used as a switch, as they deal with and spread high heat. In valves, they can be replaced after checking the voltages of the board and the network. As for semiconductors, their efforts must be measured before replacing them with a large capacity.

Among these faults are:

1- Nonlinearity defect:

A malfunction in one of the valves of this stage or in the horizontal output transformer may lead to a defect in adjusting the linearity or the straightness file. I have discussed the method of adjusting the linearity in a previous item - and the picture appears when the adjustment is not correct or when the horizontal linearity is defective, as in the figure
(17, 30) The linearity adjustment switch was found in the monochromatic valve devices. As for transistor devices or with integrated circuits, it is no longer due to its lack of necessity. The electronic circuits in the device make it impossible for him to use it.

​​​​​2 - Loss of the horizontal stimulus (horizontal leader):

The impulse circuit is what operates the horizontal output amplifier - and any malfunction in it causes the horizontal output transistor or thyristor to stop working, without any damage to it, unlike the old valve devices in which switching the horizontal oscillator valve during the operation of the device may cause the horizontal impulse to stop Hence, the possibility of damage to the output valve, and this shows the advantage of using semiconductors in circuits. And we must remember that the defect shown in the left part of the screen is generally due to a defect in the damping circuit (damper). As for the defect in the right side, it is affected by the output amplifier or the switch circuit.

The image is too narrow or distorted.

The display files must be compatible in impedance with the transformer files: and any defect in this compatibility - such as the presence of a short circuit in some of the transformer files, or the width coils - shows the image as either very narrow or distorted, or in both cases​​​​​ Together, the occurrence of a short even in one winding can affect the picture significantly - especially in low-inductance windings. The image narrows slightly in the horizontal direction. It can result from a weak current in the deflection coils, and it appears in the form of two broad black lines on both ends of the screen - but if the deficiency is on one side, it has other causes. Also, the horizontal output is weak due to a defect in the output valve or transistor or. The horizontal stimulus, as well as the weak supply voltage + B in the horizontal phase, all of which cause a decrease in the width of the image and its narrowing horizontally.

There is a wide black line on the left of the screen:

This malfunction often results from a defect in the work of the damper (suppressor), so the image appears as if it is shifted from left to right. The only reason for this phenomenon is the existence of a B+ circuit opening in the booster capacitor.

No linear structure and the sound is normal:

When there is no linear structure (raster) and the sound is normal, we follow the following scheme:

1- The light switch and the contrast switch are placed at their highest end.

2- We measure the high voltage with an RF meter and follow the following table: Table (31-17).