طريقة تتبع وكشف اعطال جهاز التلفزيون الملون والعادي ٢_a .

1- The image has lost its colors and appears clear in black and white:

The appearance of the correct and clear picture in black and white indicates the integrity of the following sections: the image detector - the image enlarger - the image driver - the red - green - blue color output amplifiers. The absence of all colors indicates that there is a defect in the circuit that passes or adjusts all color signals - so the defect may be in the chroma bandpass amplifier or color killer, the burst amplifier, the color signal carrier oscillator (4.43 MHz), or (3.58) MHz in the NTSC system:

2- Twice the color intensity:

This is due to the weakness of all colors and not in one specific color - this generally means that the two rates of the X signal receive a color signal lower than its normal level, as well as to the G-Y amplifier matrix - and the stage or section that can spoil and reduce the level of the color signal is a beam-pass amplifier Color, Color Killer or Color Splash Magnifier, check the Color Control settings.

3- Loss or poor color synchronization:

In this case, the synchronization of the monochrome image is good and correct, so the defect in the color synchronization is due to an incorrect page and the frequency of the color signal in the oscillator - (4.43 MHz) or (3.58 MHz), and this is related to the burst amplifier circuit. A circuit (AFC) (adjuster page frequency in color or oscillator

(4.43 MHz).


4 . Incorrect hue:

This malfunction is due to the mismatch of the 4.43 MHz oscillator page with the transmitted color splash signal. Must of course | making sure . Correct setting of the color hue in the first place - and the sections that may lead to this phenomenon of color malfunctions are the color pass bandwidth amplifier (error) in the adjustment or calibration of the color splash amplifier - the AFPC circuit of the color or the oscillator
(4.43 MHz) or (3.58 MHz) according to the NTSC system.

As for the faults that may arise in the luminance channel, they do not lead to one of the following phenomena:

1 - The absence of the image - or the loss of the linear structure (raster) in most modern devices - and among the expected reasons.

A - Damage to one of the elements of a traffic signal, such as an integrated circuit, a capacitor, or a diode.

b - A short circuit in one of these elements or a change in the value of one of the bias resistors.

2- Weakness in the image or contrast. In this case, it must be confirmed that there is no defect before the visualization detector, with the help of a signal plotter - then using the signal injector and following it up.

The most important reasons for this failure:

A - Damage to an integrated circuit with a Y signal or current leakage between the collector and the base of the Y amplification transistors.

B - Damage to one of the connecting capacitors or leakage in the filter capacitor.

C - Weakness in one of the detection diodes or a change in the bias resistance value.

​D - The contrast switch is damaged.

E - a decrease in the supply voltage.

3- Smudges in the image with poor detail and color.

This is due to a loss in the high frequency of the visual signal, which makes it less detailed and smeared. This malfunction may be due to poor concentration, high effort, or poor tuning. If we assume that all phases in the elector and medium frequency amplifiers work well - as well as the focus and high voltages, then the malfunction may be in the phases of the A signal and its causes are:

A - Partial damage in one of the signal amplification stages or bad response in the circuit due to a wrong bias.

B - a defect in the DC vehicle retrieval circuit.

C - A cut in one of the peak coils in the video signal's primary amplifier, or a cut or leakage in the capacitors associated with it.

D - Weakness in the electronic version of the screen valve cathodes.

e - Increasing the resistance of the visual detector or increasing the damping resistance connected with the coils of the top. The malfunction may be due to a short circuit in one of the screen elements. Or the arrival of a strong TV signal, which is often accompanied by an imbalance in synchronization.

4 - Increase the contrast
The image appears dark (Fig. The reason may be a short circuit in a passing capacitor or a damage in the transistor contrast control circuit when replacing it with something other than the same alternative. The other possibilities are due to an increase in sun enlargement
They are:

A - A defect in the AGC automatic gain control voltage.

B - Increase the magnification of the visual signal in the signal stages of L or the bias of the screen valve is incorrect.

C - Shortage or leakage in one of the link capacitors or pass capacitors connected to the radiators.

D - a defect in the continuous vehicle recovery circuit DC.

E - the sound overlaps with the image.

Bars or scales appear that ripple over the image according to the sound changes and stop when the sound stops momentarily. One of the reasons for this holiday.

A - A defect in the 55 MHz signal traps, i.e. the medium frequency of sound, or their misadjustment.

b - A breakdown in one of the elements of the trap such as the parallel or series capacitors connected with it.

C - A defect in the middle frequency section of the audio or in the Y signal channel.

6 - Image negative

That is, the white details appear in black and the black details appear in white Figure (21-24) The reason for this malfunction is the arrival of the visual signal in an opposite phase to the screen fast, and one of the possible causes.

A- Shorting one of the transistors in section A or cutting one of the serial pin coils in the integrated circuit device.

B - Significant weakness in the phase feeding voltage of the signal Y.

C - A defect in the DC vehicle retrieval circuit.

D - Leakage in one of the linking capacitors in the Y channel, or improper bias of one of the phases of the signal.

e - Malfunction in the AGC circuit

And you must remember that this malfunction may be caused by the voter or the medium frequency stage, in addition to the AGC circuit, which may have to be disconnected to determine the exact location of the fault, noting that the AGC voltage ranges from 2-3 volts, and it often requires the use of a signal oscilloscope and a signal generator.

7- The presence of an echo or resonance on the image, as in Figure (21-31), and this phenomenon is caused by an increase in the response to frequencies in the Y channel. To determine the location of the defect, we use a square signal injector at the entrance to the L channel. Follow-up with the signal and note the presence of resonance on the square signal. The most important reasons for this malfunction are:

A - Damage to the top coil or a break in the parallel resistance of the coil.

b- A defect in the signal delay line for L or the replacement of one of the elements with a non-alternative one.

C - Changing the value of the frequency response correction resistance or opening a capacitor in a circuit
one of the traps.

D - Opening the circuit of the capacitor passing the radiator or increasing the resistance of the radiator.

E - A significant increase in the resistance of the visual detector load.
​​​​​​f - Weakening of the y-channel electromagnetic veil .

8 - The appearance of return lines - they are in the form of thin white lines between them about 3 cm, and they appear due to the non-extinguishing of the returned beam. The main reasons for this malfunction are:

A - Damage to a transistor or an integrated circuit in the Y signal processing stage.

b- Opening the RC link circuit or cutting off the path of the extinguishing pulses.

​​​​​​​​C - Continuous vehicle recovery circuit fault - or weak Y signal

F - Damage to the lighting or contrast control circuit.

e - Malfunction of the screen valve due to a short circuit or leakage between its elements