The picture on the TV disappears
New generation LED-backlit TVs are very different from older models assembled on vacuum picture tubes. In them, not only the principle of operation has been greatly changed, but also the system and signal processing algorithm have been changed. And although the structure of the circuit has become more complicated, reliability and durability have increased significantly. And the quality is an order of magnitude higher, while energy consumption has decreased significantly, and the wear of radio components has decreased.
The only thing that has gotten worse is that the fragility of the screen has increased. The monitor matrix is less durable compared to a cathode ray tube. A constant advantage is the absence of high voltage.
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The most common reasons why the picture on the TV disappears
In the same way as in older generation TVs, in new models, troubleshooting should be determined based on the structure of signal processing. Starting with the output stages. If we classify the causes of this malfunction, then it can be hidden in three main components:
- malfunction of the monitor with the backlight system;
- malfunctions of the signal processing system with peripherals;
- malfunction of the power supply or filter capacitors.
And although some components and parts, peripheral and filter elements serve as auxiliary ones. The malfunction may be hidden in them. Once 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 out the supply voltage, cannot be completely removed. They must be replaced with analogues with the same or better characteristics.
The cause and its elimination depending on the characteristics of the breakdown
Using a breakdown search algorithm, you can not only identify, but even eliminate it. In many cases, having identified the problem, you can know what repairs to expect. Is it worth transporting the device, or can the defect be fixed on site? Also determine what qualifications a specialist can handle to repair this type of fault.
EXAMPLE: pEven a schoolboy who attends an amateur radio club can repair a swollen capacitor. But even an electronics engineer may not be able to cope with the task of replacing the cable. This requires specialized equipment and experience.
The image disappears along with the sound
Logically speaking, according to the algorithm, the fault cannot be in the backlit monitor. Otherwise, they would never light up, or some would light up, but because they were faulty, the controller would turn off the rest. But if the sound also disappears, then the fault is hidden in the signal processing system or power supply.
First you need to check the connector from the power supply. The contacts should not be oxidized and the pins should be securely soldered.Next, you can take a 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 “float” or “jump” and correspond to ±10% indicated on the board.- Next, you need to check the signal processing system. But here you cannot do without knowledge and equipment, so only the integrity of the parts and conductors of the printed circuit board is checked visually.
- You should pay special attention to peripheral devices, namely the connectors through which the signal passes. If they are damaged, they must be replaced. Re-soldering the connector costs much less than those nerves that will be “frayed”, waiting for a more expensive breakdown.
NOTE! If the indicated methods fail to identify the malfunction, then the TV must be taken to a specialized center for repair.
The picture disappears, but the sound works
This is the most “terrible” malfunction. It says that the peripherals and the signal processing board up to the separation of sound from the image along with the power supply are working. The backlit monitor remains.
If the matrix itself works, but the backlight does not, then this malfunction can be eliminated, and much cheaper. LEDs can be re-soldered at any service center. You can check this by shining a flashlight near the monitor itself; if there is still an image, then you are lucky. The monitor is working! Only the backlight LEDs burned out; however, there may be problems with the controller, but this is extremely rare. Replacing a monitor matrix can be compared to the price of the TV itself.
The image appears and disappears periodically
Lucky too! If the image does appear, this indicates that the monitor itself and its backlight are working properly. Except for one type of breakdown.When some of the backlight LEDs burn out, the workers light up temporarily, and the controller then turns them off. This type of malfunction is characterized by uneven illumination of the screen at the moment 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 no burning of resistors. Check whether the microcircuits are overheating.
IMPORTANT! All checks involving touching current-carrying areas of parts should be carried out only with the power supply turned off and the storage capacitor of the mains rectifier discharged.
Capacitors that are swollen or have leaked and dried electrolyte must be replaced with serviceable ones in any case. The same applies to resistors that are burnt to the point of charring. Even if the TV works without any signs of malfunction.
