LG-42LB551V. Replacing highlighting.
Fault: there is a sound, the console reacts, but there are no pictures. precisely, the image is, we do not see it, but if you look at or shine a flashlight at an angle, then the picture is still visible. This means that the TV illumination does not work.
Highlighting of this TV LED (LED), installed 8 planks of 4 LEDs on each, total 32 pcs, failure, even one will lead to the inoperability of the entire backlight system. But how to learn, diodes burned down or problem in the control driver on the board? Usually, when the TV is turned on on the backlight connector, voltage appears for a moment. from about 170 to 280 volts, then it falls. Sometimes up to 40 volts. Sometimes less, it all conditionally and depends on the TV model.
This model works on the driver BD9486F.
The maximum highlight current is set by the saturator of the FS resistor. That’s how it works. The controller calculates the current by the formula RS = ⅓ ADIM / ILED. ADIM is a signal that is responsible for the backlight brightness when you screw the brightness through the menu you form this signal. It can be of different quantities, but since we limit the maximum brightness Suppose that its maximum value is 2V. ILED is the maximum illumination current that we want to install, suppose it is 200mA or 0,2A. According to the formula, it turns out RS = ⅓2 / 0.2 = 3.33 Ohm.
Let’s still be stronger to lower, up to 100 mA. RS = ⅓2 / 0.1 = 6.66 Ohm. That is, what to lower the maximum current, we need to increase the RS rating. Resistor RS physically. As a rule, a group of resistors connected in parallel and consistently, sometimes simply in parallel.
In this model, this is a group of resistors R811-R818 (see. scheme. To increase the resistance of the group parallel to the connected resistors, one of them must be removed, in this case, break one of the chains, I remove the R811 resistor, just shifting it.
Now let’s see how the current has changed. Indications before removal of the resistor. 91.5 mA. this is current in mode no signal. Readings after removal: 68.6 mA, a decrease of 24% is almost not noticeable to the eye, but the LED will strongly extend the life.
Do not turn on
Most often, LG TV owners have to face that the device simply does not turn on. That is, the screen does not light up, remaining dark, and the LG TV power supply does not turn on, and the light bulb does not even burn in red.
In most cases, this is due to cable breakdowns. The most standard problem of wires connecting the electrical network with a TV. damage to lived, due to the fact that the cable often occurs. In addition to the liveli, the track on the chip can be damaged, since the cable often twisted. The fact is that the digital receiver in modern conditions is a small chip covered by shielding materials. In this regard, it is collected together with the cable connector.
In this video, you know more about the repair of this TV:
The main problem of repairing such a breakdown is as necessary to do with electronic elements with exceptional accuracy. Before proceeding to correct damage, they are pulled out of the connector. As soon as it was possible to do without additional damage, the cable itself is repaired using a soldering iron and glue. Wires return to their places.
What you need to know before solving the problem
When there is a sound on the Samsung TV, there are no images. it is necessary to understand the specifics of the work of its TV:
- Analog signal comes “as is”, and digital is encoded in batch data, transmitted over the communication channel and decrypted in audio and video. That is, if your TV works with digital channels, the data loss will affect both the signal and sound. Losing the video signal to remain clean sound. this is in principle impossible. Perhaps the problem lies in the transmission of the picture from the receiver to the TV itself.
- Need to determine what the screen?! It does not show, or does not work at all (that is, the same with any lighting that is “enabled”, which is “turned off”).
But there are such situations when there is no image of LG operating TV. Or the image goes like and turns off immediately, the device decided to go out and goes out the screen without any visible cause. The consumer does not immediately understand why there is no image and what causes the reason for such a breakdown.
There are several reasons why it could darken the screen. The main ones are:
To determine the cause of the breakdown and the way to eliminate it, first of all, it is necessary to understand the general principles of the LCD devices and what the main difference between the CRL and Kinescope related to them. The scheme of the product, in particular, does not imply the presence of all kinds of posistors. In most cases, the problem lies in one place. backlight. And before the master it is worth the task of determining that it launched it. To do this, it is necessary to consider that the LCD screens are two main types:
It is important not to confuse the gas lamps of televisions and those that are used to illuminate the premises. Their device is very different. First of all check if the lamp is fed. To do this, open the rear wall of the LG TV and conduct a visual inspection, determining the operability of cables connected to the matrix. After visual inspection, they can be disconnected and check the performance by the standard method. connecting the lighting light bulb.
In some models, the backlight is carried out not one, but by several discharge sources of light. In this case, they pull out the matrix and connect it to see which particular lamps work, and which. no. If necessary, replace the distilled LED.
During repair, do not forget that there are several types of LCD screens
In other models, it is possible to disconnect the lamp from the end of the product, without any intervention in the matrix itself. The required element is covered with a special protective gasket, which is moved and drooped broken part. At its same place is set in this way. new.
Attention! When replacing lamps, it is necessary to take into account their position. It happens both top and side. In addition, there are cases where several devices are located in one cell.
Sometimes consumers are faced not just with the lack of an image, but with the presence of a strip on the LG TV screen. Such a strip can be both vertical and horizontal. It is a symptom of problems with an electrode sweep. In order to ensure the correctness of the diagnosis, it is enough to connect another product with a serviceable matrix to it. The only way to repair. Replacing the details. The same reason is most likely the appearance of a spot on the LG TV screen.
Time negatively affects fees, transistors, capacitors, fuses and other TV-apparatus parts. To specify the cause of the fault, the device should be disassembled.
Important! When suspicion of technical malfunctions of the TV arose, it is recommended to contact the LG service center.
The matrix and illumination burned out
If TV has problems with the LCD matrix or LED backlight, this is noticeable by what a sharp deterioration in the image quality occurs, its dimming.
The main signs of the breakdown of the backlight and the matrix are:
- No pictures, but the availability of sound;
- The appearance of black and white or colored stripes on the monitor;
- beating pixels, ripples;
- LG logo when you turn on the device does not appear.
Important! When a flashlight screen is a flashlight, an image on it will be seen, other problems do not need to search. this is a blurred illumination.
You can check the backlight if the TV is practically disassembled.
- the ability to check the parameters of the chain sections;
- know the basic values of the voltage of semiconductor crystals;
- Show accuracy, skill and soldering skills with air hairdryer.
In the absence of the necessary knowledge and skills, it is better not to start a free repair.
In a situation where the LG TV illumination does not work, the cost of repair will be significant, it is recommended to contact the seller of the device and demand warranty repairs.
Non-compliance with operational conditions
Failure to comply with rules of operation often leads to equipment malfunctions. Before connecting the TV and start using it, it is important to explore the manual for its operation.
The most frequent breakdown of the user’s fault of the user is a mechanical damage to the screen, which is why the matrix and backlight will be replaced.
The situation is worse when the light bulb flashes with different brightness. It is the case with a violation in the electric temperature of the TV. Other connected devices operating from independent power are involved in it.
- Dead of TV and peripheral equipment (antenna with amplifier, consoles, players and t.D.);
- Disconnect the periphery from the device.
- Enable TV receiver with a single power supply.
Advice! Faster breakage breaks when using a spare periphery.
Alternately replaces the antenna, then the block, receiver and T.D., Until the desired defective device. And if the check will show the correct operation of the periphery. breakdown in the TV receiver itself and therefore it does not turn on.
If the light bulb began to work normally, and at the same time the screen turned on. one of the additional devices is defective. It violates the electrket.
When the indicator continues to flicker, and the power supply is checked with other equipment and is working, it is worth talking about a serious way out of the TV itself.
Violations in the power circuit can be called for many reasons, you need to check in the following order:
- Heating near the video adapter. Work at the limit of power overheats it, resulting in resistance and the fuse is triggered. As a result, the TV will not be turned on for some time, and after the new heating will continue. This often happens when trying to play Ultra-HD or 4K on the screen, the resolution of which is much lower.
- “Search” in the corps smell Gary. He clearly indicates an explicit way out of order. Breakdown is eliminated only by its replacement.
- Faulty condenser. A crack or bloating on it says that the resistance of the contact material has grown so much that he did not cope with him. It is necessary to replace the damaged condenser, as well as eliminate the causes of the growth of resistance. voltage jumps or the moisture fee.
This is what a good capacitor looks like, all of them need to be checked for mechanical integrity most often from the violation in the chain of the device “suffers” the inverter, which is responsible for the color reproduction by supplying the current to each matrix LED. So the TV can turn on, but the screen will not show at all.
Advice! The check is recommended to start with the inspection of contacts and wires at the “iron” of the TV, and after it is taken for checking the block and periphery.
The problem is that when checking devices with an alternate connection makes each time a defective TV. As a result, he may be applied even more damage.
If there are skills to work with a multimeter, and the incoming voltage is known to the fees (each model is different, for example, the inverter can act 12 or 24 V, and from the decoder comes from 5 to 12 V), then the focus of the problem can be found very quickly. After eliminate violations in the power chain of the TV.
On USB Login is powered by only 1.2 V instead of the laid 5 V, which clearly indicates violation in the chain
Usually these measures are quite enough to turn on even after a serious breakdown. If the options described in the topic did not help, then the service center remains.
The malfunction may be connected with such factors as the installation of incorrect part (with unfair repairs in the past) or factory marriage. It is better to ask a question to specialists, why the LG brand TV does not turn on and contact the service center.
It does not matter a plasma or a kinescope TV, the breakdown can show itself only in such ways:
- The screen will not light up, although the indicator is lit or flashes as usual;
- The indicator when turned on immediately lights up and goes out;
- After starting, clicks, unusual sounds appear.
Look for a fault you need stages. We are paramount to inspect all the external elements, and only then internal details. We start with a remote, which often breaks down the power cable. If there are skills, you can open the TV and inspence the internal elements. If no damage is visually visible, then the diagnosis should be carried out by specialists.
The indicator is on, but TV does not start
Quite often, users are interested in why LG TV does not turn on, although the indicator is on. This happens when the device is in standby mode, it must be enabled. For these purposes, use the control panel or click on the button on the device itself.
If the TV continues to ignore the commands, and the control panel is in a completely good condition, then the breakdown is associated with the power system:
In such a situation, the power supply can show that the energy goes, but it is not enough, to start the device. In this case, you need to contact the service center, unless of course you do not own knowledge for self-repairing.
The indicator flashes
Now we’ll figure it out what to do if the LG TV does not turn on, but the indicator flashes. Practically in all LG models, before the appearance of the image, the indicator flashes red several times. If the picture does not appear on the screen, most likely, the problem, lies in voltage.
For stable operation, TV should be connected to a network with a stable voltage of 220V. Regular jumps, can contribute to the fact that protection will work. Even if subsequent voltage is given to the desired value, the device will not turn on. It will be necessary to completely disable from the network for 30 minutes, and then re-run. Although this approach will help not with all models, only the master can be disconnected in some. You can avoid such problems by installing special protective devices, such as voltage stabilizer.
The indication is completely absent
If the TV is connected to the power grid, but the signs of life does not submit, most likely, it will be required to be attributed to. However, pre-give attention to the following factors:
- Power button. All models are equipped with a power button. It is near or close to the power indicator. To turn on the TV, it is enough to press it. After that, the indicator should start glowing with a red or green tint, and the device itself will respond to commands from the control panel.
- Sleeping.LG is worried about its customers, making its devices as cost-effective. Therefore, in the last models there is a power saving mode. It is activated automatically, after a few minutes of idle. Also sleep mode is triggered if the AV / HDMI / TV active connector is running.
- Voltage in the power supply system.Check the performance of the outlet to which the device is connected. Connect another electrical appliance to it or use the screwdriver indicator. If special protective devices are used from voltage drops or extension cords, be sure to check their performance. And it is necessary to check not only the devices themselves, but also the wires.
If all these actions did not give the result, then the TV requires professional diagnostics. It is quite possible to fail the power supply or broken the motherboard.
If, when you start TV, various specific sounds, clicks, the display is not turned on long, then:
Worked the protective lock, this can happen during a thunderstorm.
Completely fuse. And such a breakdown is characteristic of all LG TVs.
Quite often, the breakdown is happening after a strong thunderstorm, since it is in this period that strong voltage jumps are observed. As a result, the protective lock is triggered, eliminating serious damage to the chip. Only experts will be able to repair the TV.
It should also be noted that LG Smart TV models running on the WebOS platform can be broken due to software error. It happens, it is after unsuccessful installation update.
The problem is solved quite simply. the working firmware is installed from the flash drive. Certain this can any user. Carefully learn the instructions for TV, get acquainted with the recommendations on the Internet. If we are categorically not confident in your abilities, then it is better to immediately call the masters.
In our service often receive calls from people who face a problem when the remote control switches the channels. The most popular causes are inattention or improper operation of technology.
To reduce the likelihood of breakdown, we have developed several recommendations:
- In the absence of a reaction to remote commands, be sure to check the presence and correctness of the installation of batteries.
- If the batteries oxidized, remove them, wipe the contact groups from alcohol contaminants and put new.
- If the TV is installed in the kitchen near the plate or exhaust, wrap the PO Celofan or buy a special plastic shrink package. So you can protect the internal elements of the design from the fall of fat, moisture and other foreign objects.
- SMART TV owners can download a special program to their tablet or smartphone, which will allow you to control the device from your gadget (a great option in case of breakdown or loss of the console).
Observing these rules and carefully referring to the technique, you can significantly reduce the frequency of the appearance of various breakdowns and prevent the appearance of defects due to the fault of their own negligence.