TVs of the new generation with LED-backlight are very different from old models assembled on vacuum picture tubes. They not only greatly changed the principle of operation, but also changed the system and signal processing algorithm. And although the structure of the circuit has become more complicated, reliability and durability are increased significantly. And the quality is an order of magnitude higher, while the energy consumption has decreased significantly, the wear of radio components has decreased.
The only thing that got worse was the fragility of the screen. The monitor matrix is less durable than a cathode ray tube. Invariable advantage - the absence of high voltage.
The most common reasons why the picture disappears on the TV
In the same way as in older generation TVs, in new models, troubleshooting should be determined based on the signal processing structure. Starting from the weekend stages. If we classify the causes of this malfunction, then it can be hidden in three main nodes:
- malfunctions of the monitor with the backlight system;
- malfunctions of the signal processing system with peripherals;
- malfunctions of the power supply or filter capacitors.
And although some components and parts, elements of the periphery and filters serve as auxiliary. A malfunction may be hidden in them. After they are completely removed, the TV can work great for many years.
IMPORTANT! Varistors and capacitors that prevent peak voltage surges, however, like capacitors that smooth the supply voltage can not be completely removed. They must be replaced with analogues with the same, or better characteristics.
The cause and its solution, depending on the characteristics of the breakdown
Using the breakdown search algorithm, you can not only determine, but even eliminate it. In many cases, having determined the malfunction, you can know what kind of repair to count on. Is it worth transporting the device, or can the defect be fixed on the spot. Also determine what qualifications a specialist can handle repairing this type of malfunction.
FOR EXAMPLE: nThe swollen capacitor can also be repaired by a student who attends a hobby club. But the electronics engineer may not even be able to replace the loop. Specialized equipment and experience are needed here.
The image disappears with the sound
Logically arguing, according to the algorithm, the malfunction cannot be in the backlit monitor. Otherwise, they would never light up, or a part would light up, but due to malfunctions, the controller would turn off the rest. But if the sound disappears, then the malfunction is hidden in the signal processing system or power supply.
First you need to check the connector from the power supply. The contacts must not be oxidized and the pins are firmly soldered. Next, you can take the tester, set the measurement limit to at least 100 V, and measure the voltage at all terminals of the output connector, relative to ground, COM. The voltage should not “swim” or “jump” and correspond to ± 10% indicated on the board.- Next, you need to check the signal processing system. But here you can’t do without knowledge and equipment, therefore only the integrity of the parts and conductors of the printed circuit board is checked visually.
- Particular attention should be paid to peripheral devices, namely to the connectors through which the signal passes. If they are damaged, they must be replaced. Soldering the connector is much cheaper than those nerves that will be "frayed", expecting a more expensive breakdown.
First you need to check the connector from the power supply. The contacts must not be oxidized and the pins are firmly soldered. Next, you can take the tester, set the measurement limit to at least 100 V, and measure the voltage at all terminals of the output connector, relative to ground, COM. The voltage should not “swim” or “jump” and correspond to ± 10% indicated on the board.NOTE! If the indicated methods failed to identify a malfunction, then the TV must be taken for repair to a specialized center.
The image is lost and the sound is working
This is the most "terrible" malfunction. She says that the peripherals and the signal processing board, until the sound is separated from the image, together with the power supply, are working. There is a backlit monitor.
If the matrix itself works, but there is no backlight, then this malfunction is eliminated, and much cheaper. Solder LEDs can be in any service. You can check this by shining a flashlight near the monitor itself, if you still have an image, then you are in luck. The monitor is working! Only the backlight LEDs burned out, although there may be problems with the controller, but this is extremely rare. Replacing the monitor matrix can be compared with the price of the TV itself.
The image periodically appears and disappears
Lucky too! If, nevertheless, an image appears, this indicates the serviceability of the monitor itself and its backlight. In addition to one type of breakdown. When part of the backlight LEDs burn out, the workers light up for a while, the controller then turns them off. This type of malfunction is characterized by uneven illumination of the screen at the time the image appears.
Most often, such a malfunction is associated with the power supply or filter capacitors. To do this, it is necessary to check the integrity of all electrolytic capacitors, for the presence of swelling or leakage of electrolyte from them. Also the lack of burning resistors. Check if microcircuits are overheating.
IMPORTANT! All checks with touching current-carrying areas of parts should only be performed with the power supply turned off and the discharged storage capacitor of the network rectifier.
Swollen capacitors or with leaked and dried electrolyte should be replaced with serviceable ones in any case. The same goes for resistors burnt to char. Even if the TV works without any signs of malfunction.
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