الأجهزة اللازمة لإصلاح وضبط الجهاز التلفزيوني الأحادي اللون والملون ١_a .

Chapter XXI

Devices for adjusting, calibrating and repairing color and monochrome televisions and malfunctions

1-21 Introduction to the causes of malfunctions:

Any TV device is exposed to some malfunctions for the following reasons:

1- Continuing work for several hours, which raises the temperature of some elements and damages them or changes their specifications, causing a change in the operating conditions of other circuits.

2- The power supply voltage is high or low, despite the presence of voltage regulation circuits in most colored devices.

3- Exposure to shocks, especially during work, or the leakage of some liquid materials into its internal circuits, or the fall of metal pieces such as pins and others between its components.

4- Lack of ventilation of the device, especially in hot weather, or the presence of a cover on the device during work.

E - a malfunction in one of the elements of the circuits because of his age. Or dry welding points in high temperature pieces.

6- High voltage leakage in the form of sparks due to the insulator drying out or the high voltage exceeding its correct value.

​​​​​​​​​​​​​​​​​​​​​​​In order to ensure the repair of the broken device, the technician or electronic engineer must be familiar with the circuits of the device in theory and practice, and it is preferable to have the complete diagram of the device and the printed circuit diagram, and the repair and maintenance brochure issued by the factory. The necessary devices for measurement and replacement parts must also be available Or the equation for broken elements or expected to have a malfunction. The faults may be simple and clear, revealing themselves when the shape of the faulty element changes, such as a burnt resistor, an exploded capacitor, or a bulging or cracking in it, or the appearance of sparks from somewhere. Or the appearance of a break in the circuit board. A novice technician may be able to do this repair despite his meager information and experience, and this does not qualify him to repair more complex faults that may require resetting some settings. This technician may cause. Those who are able to increase malfunctions and aggravate the defect, therefore, it is preferable not to persevere in conducting operations and experiments that are not based on understanding and awareness of the work of all the circuits of the device and its elements.

2-21 The devices required to repair and adjust the monochrome and color TV set are:

1- A high impedance multimeter such as a FET multimeter or a digitol multimeter.

2- A signal graph.

3- An RF frequency scanning generator or a line scanning generator.

4 - RF signal generator.

e - color line generator that gives cross line patterns and points or demo sample generator.

1- Pointer ohmmeter (normal):

​​​​​​​​It is one of the basic devices for repairing electrical and electronic devices. It achieves the measurement of voltages, resistances, current intensity, and decibels.. and it must be available in it Accuracy and high input impedance, and the possibility of measuring high voltages. The figure shows an ampere meter that is suitable for electronic maintenance and repair work and has these specifications
(1 - 21)

1- It measures AC-DC voltages over the same field from 0.03 to 1000 DC, A from a separate pole.

2 - Input resistance = (10 megohms) and 31.9 megohms for the 10007 field measurement.

3 - The range of DB is from 50 to 62 dB.

4 - Measures AC and DC current from 30JA µA up to 14 and 104 from a separate outlet .

e - measures resistance from 0.22 ohms up to M2 (1000 megohms) and has two LED indicators for polarity on both ends of the left number plate. electricity or battery.

Digital ohmmeter:

This scale is very practical because it exceeds the disadvantages of the pointer device in terms of accuracy, clarity of numbers, and distance from the risks of misuse. The specifications of the device shown in the figure are:

1- It measures DC voltage from (0.2) to (1000) with positive or negative polarity.

2- It measures AC voltage from 40 Hz to 20 kHz) from (0.2) to (600).

3 - Measures low resistors from 10 to K2 2000 from 10 to 2 MHz.

4 - Measures high resistors from 1 ohm to 20 MHz.

5 - measures the intensity of the continuous current from 0.2m to (10.0m).

6 - Measures the intensity of alternating current (from) 0.2mA to 10

It has an additional measuring cable to measure up to 40000 V, and an additional RF measuring cable to measure RF voltages up to several hundred megahertz.

2- Oscilloscope:

It is an important device in the repair, maintenance and tuning work of monochrome and color television, and some of its uses.

1- Observing the specifications of the pass band in the voter and the stages of the average frequency of the image.

2- Monitor the image detector signal.

3 - Monitor the synchronization and extinguishing pulses.

4 - Observe the color splash signal on the back sill of the horizontal extinguishing pulses.

e - Observing the color amplifier beam-pass.

6 - Use the device as a DC voltmeter and AC peak-to-peak measurement when measuring the waveform of the signal. Figure (3-21) shows a dual-effect signal oscilloscope device that is suitable for maintenance and tuning of the normal and colored device, and has good specifications. Refer to the accompanying device instructions.