LED backlighting is now used in most modern TVs. LG televisions are no exception. Although the company is famous for its high quality products, breakdowns still happen. And most often the backlight fails. It is worth repairing the backlight in Russia from 1,000 to 12,000 rubles.

What's this?

By repairing the backlight on an LG TV, we understand the replacement of failed elements with new ones. This work is very painstaking, carried out in certain conditions. Therefore, it is better to contact the telemasters.

The following signs indicate that you need to repair the backlight:

  • When the device is turned on, there is no image (a black screen with barely noticeable silhouettes), while there is sound, you can switch channels, change the volume.
  • Dark spots appeared around the edges of the screen.
  • The image is flickering.
  • When watching a movie, my eyes start to hurt a lot.

The backlight fails for the following reasons:

  • The inverter driver is broken.
  • The lamp in the matrix burned out.
  • The correct functioning of the backlight module has been disrupted.

A competent specialist is able to determine what exactly is the cause of the breakdown.

Restoring the backlight on an LG TV goes like this:

  1. The master goes to the house or the client brings the faulty device to the service center.
  2. The TV is being diagnosed.
  3. After identifying the cause of the breakdown, the master negotiates with the client the cost of the work and the timing of its completion.
  4. The backlight is being restored (the TV is disassembled, the matrix is ​​removed, non-functioning LEDs are replaced, equipment is being assembled).
  5. The TV device is checked.
  6. The client pays the master and receives a guarantee sheet.

In time, work can last from 2 hours to several days. It all depends on the number of failed LEDs. In addition, spare parts for LG TVs are not always available.

What does the price depend on?

Repairing the backlight on an LG TV costs a different amount of money. When setting prices, service companies take into account the following:

  1. TV Diagonal.
  2. Technology model.
  3. Availability of a warranty card.
  4. The number of failed LEDs.
  5. The complexity of the work.
  6. Screen diagonal.
  7. Diagnostic cost.
  8. Year of manufacture of the TV and its general condition.
  9. The price of spare parts, accessories.
  10. The need for a home visit.
  11. Qualification level of the telemaster, his experience.
  12. Order urgency.
  13. The prestige of the service telecenter, the pricing policy used by it.

The more LEDs burned out, the more expensive it will be to repair an LG TV. The complexity of the work, the departure of the master at home, the urgency increase the cost. Prestigious service centers offer a higher price list for their services than little-known companies.

Repair types

Depending on the number of failed LEDs, there are two types of repairs:

  • Replacement of individual LEDs.
  • Replacing the entire matrix.

From the time that the customer allocates to the master for work, repairs can be:

  • Non-urgent.
  • Urgent.

Depending on who repairs the TV:

  1. Professional.
  2. Independent.

Approximate price

Repairing the backlight on an LG TV costs about 1,000-12,000 rubles in Russia. Much depends on the diagonal of the screen. The cost of repair work depending on the diagonal:

  • up to 31 inches - from 1000 rubles.
  • 32 to 36 inches - about 2500 rubles.
  • 37-49 inches - 3800 rubles.
  • 50-59 inches - from 5000 rubles.
  • 60-74 inches - 6000 rubles.
  • over 75 inches - from 12000 rubles.

From whom to order a service?

To repair the backlight of an LG TV, you need to have certain knowledge and experience. Therefore, it is not worth taking on such work on your own without certain skills. It is better to contact the professionals of the service telecenters. Competent specialists work there, the client is given a guarantee sheet for the service rendered.

If the price of restoring the working capacity of a television device seems too high, then you can look for a good master among private traders. But you need to understand that such specialists do not provide a guarantee for their work. This can cause a number of problems when proving the fault of the master in poor-quality repairs.

I also wanted to ask you about the "PMS" contact, which goes from the main board to the power supply or vice versa, from the power supply to the main board. Can't figure out his role?
I'm interested in this, because I also want to disable it. I will hang the monitor on a swivel arm and want to power it from a standard TFX power supply from a mini case, in which it will be assembled new computer for parents (with not very new components, with DDR3L memory and intel processor 3rd generation :). Today I conducted an experiment, applied 5V, 12V and minus from the floppy drive connector from the computer power supply. The monitor worked fine and surprisingly even turned on and off with the power button (I believed that PMS sends a signal to the power supply to turn off the power to the inverter or the inverter and the main board at the same time). It’s just that the monitor will hang over the bedside table and there is just enough space there, so it’s much easier for me to power it from the power supply, especially since I built a two-phase switch into the power supply, which turns off zero and phase at the same time (that is, the computer is no longer needed unplug). And if you run a separate 220V cord to the monitor, then this is more wires, plus more hassle with turning it on / off, and the efficiency of the power supply will not be much lower (total energy consumption when powered from the computer's power supply will decrease ~ 5-10 watts). Power supply with "GOLD" certificate, Sea Sonic Electronics SSP-300TGS Active PFC 300W. Therefore, I need to know what the "PMS" signal does, wouldn't its absence on the monitor's power supply be critical?

I also did an experiment with "PMS" today. This pin is supplied with 2.794 volts and only when the monitor is running. If the monitor goes to sleep or is turned off using the button on the front panel, then "PMS" immediately drops to zero. And it also turned out that the first coil produces 5 volts 1.5 amperes, and the second one simultaneously produces 12 volts 1.2 amperes (to power the main board) and 12 volts 3 amperes (to power the inverter). That is, with any shutdown or sleep of the monitor, 12 volts disappear from both lines, and 5 volts are supplied all the time while the monitor is plugged in and the main switch supplies 220 volts to the power supply (apparently 5 volts goes both as power to the main board and at the same time they are needed to wake up the monitor from standby).
So most likely "PMS" still comes from the main board to the power supply and is needed to run a highly powerful coil, but still I want to know the opinion of an expert, since I only judge from practice and from logical guesses.

And if possible, I have three more requests for you.
1) You cannot look at the 12 volt circuit that comes from the power supply to the main board, it's okay that 12 volts will be constantly supplied during sleep or when the monitor is turned off through the button on the main panel. As I wrote above, 5 volts work constantly from the built-in power supply, but 12 volts are supplied only while the monitor is running. I just want to make sure the 12 volts don't damage the main board while sleeping or turning off the monitor.

2) In addition to supply from system block, I want to implement a dimmable LED backlight using variable resistance to avoid PWM diodes at low brightness (flicker). I understand that the diodes will heat up more, efficiency will drop (energy consumption will slightly increase), but eye health is more important. I myself do not know how to correctly calculate what power variable resistor needs to be put in the circuit. According to the manufacturer, the energy consumption of the tape is 9.6 watts per meter. The tapes are cut with a distance of 5 cm, and my matrix needs two strips of 45 cm each, that is, a total of 90 cm. And according to the manufacturer (which I do not really trust), the consumption at 12 volts is 800 milliamps per meter of tape, minus 10% = 720 milliamps. But it is better to take a resistance with a good margin of power, at least 2-3 amperes. I would also like to put in the chain additionally conventional resistance so that at maximum brightness (where the variable resistance supplies power to the direct line), not 12 volts go to the diodes, but 10.5 - 11 volts, no more. This is necessary so that the diodes do not overheat at maximum brightness, as well as increase their service life, since it is still a pleasure to completely disassemble the monitor and the matrix box once again.

If it’s not difficult, then write the number or model (I don’t know how correctly) of variable resistance (you need with a handle, like a volume acoustic systems, because in the back of the monitor there is a good place, where it can be brought out) and how many ohms (even more likely kOhm) and watts to take a "simple" resistance, which will additionally lower the voltage from 12 volts to 10-11 volts.

3) You also need to find a place in the power circuit of the main board, from where you can take 12 volts to power the diode backlight, where power will be lost when the monitor is turned off with its off button and sleep mode. I myself can find 12 volts as a tester, which disappear when the monitor is turned off and asleep, but I'm afraid suddenly they pass through some kind of resistor or transistor, which can burn out from an additional load of 0.7-.08 amperes.

For several weeks now I have been building the most compact computer with standard components (that is, a standard power supply, a standard motherboard, processor, OP memory, even the presence of a laptop DVD drive there is). He brought the missing "RESET" button, the missing indicators to his face, replaced the terrible blue indication of computer operation with a warm orange one, put the DVD drive switch (so that it would not make noise unnecessarily when the computer was turned on) and the amplifier with speakers, and also attached the amplifier itself to the face and volume control. It only remained to wait for the dust filters to arrive on the case and the power supply and a 6-pin connector to bring the speakers out of the case and indicate their operation. I plan to fasten the speakers to the bottom of the monitor case, and bring the indication of their work to the bottom of the case of the speakers themselves (both of them will have the lower plexiglass glowing during operation). I was already glad that there was a little hemorrhoids left before the assembly of this Frankenstein was completed, and then they call me and say that the monitor has stopped working. It was a huge ambush :(
That's why I want to do everything as reliably as possible, so that it works for a long time and does not cause more trouble for at least 10 years o_O.

P.S.
Sorry for the abundance of questions, I'm just afraid to burn the main monitor board out of ignorance. Considering that this model has not been produced for more than 10 years (and as I already wrote, there are no alternatives to it, of the modern ones there are only two models on IPS matrices, they have been doing it on VA for a long time, especially on PVA), and it’s almost impossible to buy the same used one in good condition (in Moscow and St. Petersburg they occasionally appear on sale). But if you buy it remotely, you will get any darkening or scratches of the matrix, as well as broken or burnt out pixels. When I bought the second 2190UXp through Avito, the seller from St. Petersburg assured me that the matrix was ​​ideal, and when the monitor arrived, it turned out that the lamps had sat down to zero (apparently for this reason I sold them so that they didn’t finally get screwed up) and as a bonus from above, I I got two dead pixels (fortunately, at least the pixels are not in the center of the screen and on the VA matrix they are not so noticeable, the parents do not notice them at all).

In the work of even the highest quality equipment, various failures and malfunctions appear. Therefore, each user must be prepared to have to repair the equipment with their own hands, because you can go broke on paying for the services of service centers.

Today we will talk about the most popular breakdown - a malfunction of the LED backlight on LG TVs. It is with this problem that ordinary users most often turn to service centers. Few people know that you can normalize the operation of the device on your own. Special skills are not required, the main thing is to follow the instructions.

Before you start repairing the LG TV backlight, you should first figure out how this component works, what are its functions and why is it needed at all?

What is LED backlight?

The abbreviation LED stands for Light Emitting Diode, which translates from English as a diode that emits light. Speaking specifically in the context of the television equipment manufacturing industry, this abbreviation refers to the type of liquid crystal matrix and light emitting diode backlighting.

After the new type of LCD backlight was introduced, manufacturers began to replace the abbreviation LCD in the name of the models with the designation LED. Of course, LG TVs are no exception to this rule.

In fact, the motive for such changes was more of a marketing goal than a real need. The fact is that LED backlight matrices is not fundamentally new technology production of screens for television equipment. It's just an updated way of lighting. However, the trend took root harmoniously, so the term Light Emitting Diode is actively used today.

The most common TV matrices are based on the use of a cold cathode lamp, in fact they are all the same fluorescent lamps. As for the LCD and LED models, they are characterized by light-emitting diodes.

It's no secret that LCD screens are made up of pixels with liquid crystals. The position of the crystal in the pixel determines whether the cell transmits light. Actually, this is how the screen glows.

The quality of the screen matrix determines great amount parameters, in particular: the level of dark shades, viewing angle, static contrast, image refresh rate and even response time. Liquid crystal matrices are produced using several technologies. We list the most popular: TN, IPS, PLS.

As for the backlight itself, it affects the brightness, color reproduction, coverage, dynamic contrast. However, it is still worth evaluating the parameters in the complex, taking into account the type of matrix and backlight.

Thus, buying a TV with LED backlight, the user receives:

  • balanced contrast;
  • saturated brightness;
  • high definition picture;
  • color palette.

In addition, LEDs consume much less electricity, by about 40%, than their counterparts. Directly fluorescent lamps, which are also used in the production of television equipment, contain mercury, which negatively affects the environment. In this regard, the advantages of LED are obvious.

There is no point in arguing that modern TV devices with backlighting consisting of LEDs provide the broadcast of the brightest image. Dynamic contrast appears - regulation of the brightness of the diodes for different parts of the monitor. The image becomes more realistic.

Adjusting the glow of the diodes directly in the process of watching TV has a positive effect on the black level. When dark shades appear, the backlight level is lowered, resulting in a darker screen.

Causes of backlight failure

High-quality television equipment is able to work for a long time, so backlight problems appear after an impressive period of time. Unfortunately, the same cannot be said about Chinese manufacturers.

Why is there no backlight? There are several reasons for the appearance of a malfunction, we will analyze each of them:

  1. A certain line of diodes burned out. LEDs are characterized by a serial connection type, which means that if one element stops working, then the entire component fails. However, the voltage (about 200 volts) continues to flow to the light bulbs.
  1. Problems with the LED driver. The image disappears on the LG TV due to the fact that, on the contrary, voltage is not supplied to the LEDs, respectively, they do not light up.
  1. Manufacturing defects. Sometimes only one LED does not work, but the screen of the TV device does not light up.
  1. The user sets the maximum brightness of the image, which leads to an increase in voltage, as a result, the diodes do not withstand and burn out.
  1. Sometimes incorrect settings for the voltage supplied to the LEDs are the fault of the store where you purchase the TV. They try to attract buyers with a bright picture.

Now you know why the LED backlight of the TV fails. This breakdown is quite common, but if you follow the manufacturer's recommendations, you can significantly extend the life of the device.

Professional repairmen using special equipment will determine which module is out of order. How ordinary user understand that the backlight of the LG TV screen does not work? Now let's look at the basics of diagnostics.

TV Diagnostics

How to determine that it is the backlight that has failed? It all depends on the symptoms. For example, an LCD TV is started from the remote control remote control, but there is no image on the screen. Point a flashlight at the screen, as a result you will see a dim picture. In fact, the flashlight performs the functions of forced illumination.

Based on this, we conclude that either LED driver or backlight. To specify the source of the problem, you should disassemble the TV and carefully examine the elements of the hardware component.

Remember that you should only disassemble the TV case if you have had a similar experience before. If there are no skills, then it is better to contact the service center. Once again, it's better not to risk it. Since there is always a chance to make things worse, that is, to aggravate the initial breakdown.

To dismantle the back panel of the LG TV device, simply unscrew the special bolts that provide fixation. It's easy to do. First disconnect the supply and dismantle the fasteners. If the cover still does not come off, then you need to find the blocking bolt.

When the back panel is removed, you should check the backlight and the output voltage. For example, if the backlight voltage is 100 volts, then the component is out of order.

In most cases, LG TVs are equipped with an LED lens array that sits around the entire perimeter of the screen to provide clear illumination. To get to this part and fix it, you must first dismantle the matrix.

Now you know what to do if the TV turns on, but there is no image.

Product disassembly

Regardless of the model, television equipment is equipped with three key boards: main, T-con and power adapter. Immediately after removing the cover, you will see them.

Disassembling an LG LCD TV is an extremely difficult and time-consuming process, be very careful as there is a risk of damage to other hardware elements. To carefully disassemble the TV, follow these guidelines:

  • prepare in advance the working area and two closely spaced tables on which the components will be placed: matrix, LED strip, bar;
  • Before starting disassembly, wash your hands to avoid contaminating the filters or the matrix. In the future, this will negatively affect the quality of the image;
  • special attention should be paid to decoders, if you are not careful, you will simply cut off the cable.

Step-by-step instructions for disassembling television equipment:

  1. Disconnect the cables and unscrew the bolts located between them to disconnect and remove the T-con board.
  1. Remove the metal protective elements from the decoders. To do this, unscrew the fasteners located on the sides and the bolts. As a result, the decoders will be held solely on rubber mounts.
  1. It's time to remove the front bezel of the device. Unscrew the screws around the perimeter and place the product on the back panel. Remove the frame.
  1. Flip the screen while holding the matrix. The decoders should be on top, you can disconnect the rubber fasteners that hold them, the main thing is to do everything very carefully.
  1. We disconnect the matrix and put it on a pre-prepared table so that it does not interfere with the backlight repair.

In principle, anyone can disassemble a TV device, the main thing is to be as accurate as possible.

Determination of non-working LEDs

Previously, we examined the process of disassembling the TV, now we will proceed directly to the repair. To replace the LEDs in the backlight, carefully snap off all fasteners, and then dismantle the plastic frame. We remove scattering films in order to open access to faulty elements.

The structure of the LED backlight directly depends on which model of television equipment we are talking about. For example, for LG 32LB582V there are three rows of LEDs for 6 pieces. Model 32LN541U has one more diode per row.

Television equipment that uses this lighting technology is characterized by a serial connection of diodes, so if only one element burns out, then the entire system will fail.

In the event of a driver failure, voltage will cease to flow to the entire system. If only one diode burns out, then there will be voltage, but there is no proper lighting. The circuit is open. Therefore, you need to change the faulty LEDs of the LG TV for correct viewing.

Approximately the backlight system has about 18 diodes, voltage measurements showed that 140 V is supplied without loading, which means that each element individually accounts for approximately 7.8 V.

What are all these calculations for? The voltage level of each bar and the total load allow you to calculate the power of the LEDs used. It is extremely difficult to find a faulty element of the system. If the mounts are not burnt, then you will have to double-check absolutely all the diodes one by one.

Replacing LEDs

It is extremely difficult to replace the backlight of an LG TV on your own, it is possible that you will have some difficulties. Suppose that during the diagnostic process you were able to identify a couple of damaged diodes. Buying a bar of new light bulbs is very problematic. Service centres do not supply these parts, so the only way out is to purchase from the manufacturer. It is clear that the delivery will have to wait a very long time, not to mention the cost.

In order not to buy a bar, you should replace the LEDs in LG LED TVs one by one. You can buy on the market. Mostly already soldered parts are sold, but it's okay, the main thing is that they work.

Remember that absolutely all slats are fixed with double-sided tape. Therefore, they need to be heated with a soldering dryer to loosen the fixation of the adhesive tape. Fix the LED strip in a special holder. Heat it with a hair dryer from below, as a result, the tin will be melted. So the broken part is removed. Soldering is carried out in a similar way, the only way to change the part, while not damaging it.

Remember that in the factory, absolutely all lenses are attached with a compound, therefore, in the process of dismantling them, be extremely careful. Each of them will have to be installed in its place. To keep focus.

There is one more subtlety: it is possible that you will come across LEDs with a large negative area, therefore, the positive one will be smaller. Cut the contact point to solder the diode.

In the event that the paint is slightly damaged - it's okay. The remaining structural elements are soldered according to a similar principle. As for the lenses, they need to be glued with superglue.

Note.

The ability to do something with your own hands, as well as repair electrical appliances, remains relevant today. It is much cheaper to replace a damaged part yourself than to pay for the work of a professional repairman. And often the repair is not so complicated as it seems at first glance. In today's article, we will consider such a situation as replacing old lamps in a monitor with a more modern lighting product - an LED strip.

Monitor with LED backlight

In order for such a replacement to be successful, you need to know the sequence of actions, as well as some of the nuances that will be discussed in this article.

Reasons for changing the light source

To date, LCD monitors with a backlight are actively used. They replaced older models of monitors that were less well made. Despite the rather high level of technology, in some cases such products are equipped with backlighting, organized using old-style lamps. And, as you know, the old light sources did not differ in a long period of work. Because of this, very often it is the backlight that fails in such electrical appliances. This breakdown is not so difficult for the monitor to seek help from specialists. If desired, all repairs can be done by hand.

LCD Monitor

It is worth noting that despite the presence of a large number of monitor manufacturers, such devices operate according to a single principle. This is very convenient, because knowing the principle of operation of one monitor, you can relatively easily repair another model from another manufacturer. Therefore, if you did not find the necessary part when disassembling it in the usual place, you should not worry, it is probably hidden nearby and with due consideration you will definitely find it.

Why change to led?

To date, the most modern and advanced light sources are LED products. Moreover, LED strips have become the most widespread.

LED Strip Light

In a situation where it is necessary to replace old used lamps in the monitor, the choice falls precisely on given type products for the following reasons:

  • long service life of LEDs. At correct connection they are able to work without a visible decrease in the brightness of the glow for almost 10 years! Such a service life of this moment no other light source can boast;
  • such tapes have a self-adhesive backing, can be easily attached to any surface, even back monitor;
  • LEDs give a bright luminous flux, which is well perceived visual analyzer person. When working for a long time behind a monitor with LED backlight, the eyes practically do not get tired;
  • the glow of the backlight can be absolutely anything;

Note! Despite the presence large selection ribbons according to the type of glow, it is recommended to choose more calm and neutral colors (for example, white or yellow) for the backlight of the monitor.

The glow of the LED strip

  • LED strips are sold in a coil of 5 meters. This length is quite enough to create an effective and high-quality monitor backlight;
  • relative ease of connecting the product in the electrical appliance board;
  • low power consumption with high fashionable light source. Typically, LED strips operate at a voltage of 12 or 24 V;
  • the absence of strong heating of the diodes during operation. This is very important point, since it is due to severe overheating that the lamps originally built into the monitor design fail. It is worth noting that old-style lamps still often fail due to frequent on / off electrical appliances. But for LEDs, this is not such an important parameter;
  • the resistance of the tape to mechanical and vibrational influences, which minimizes the risk of damage to the backlight during the operation of the device.

As you can see, replacing the old lamps in the monitor with a more modern LED strip will give a large number of good points in the future, use the repaired monitor.

Assessment of the complexity of the breakdown

Before proceeding with the installation of the LED strip in the monitor, it is necessary to disassemble it and evaluate the degree of its performance. There are situations when not only the backlight burned out in the device, but also the failure of other important components of the electrical circuit. To identify all the existing problems and generally evaluate the possibility of self-repair, you first need to unwind the monitor and find out the causes of the breakdown.

Monitor Matrix Backlight

The backlight lamps of the monitor matrix fail for the following reasons:

  • the presence of an initial manufacturing defect;
  • there was physical damage to the lamps due to the fall of the device or the impact of any object on it;
  • a short circuit occurred on the metal parts of the lamp and the matrix frame;
  • The backlight bulbs simply ran out of time and burned out.

If you unwind the monitor, you can visually determine the presence of a malfunction of such lamps, as well as determine the cause that led to this type of breakdown.
But in order to make a quality lamp replacement, you need to know the principle of operation of the liquid crystal matrix, which is built into any type of modern monitor.

The principle of operation of the LCD matrix

AT modern monitors All LCD matrices work on the principle of lumen. This means that a light source must function in the device, which will shine through the matrix through.

Note! The quality of the monitor directly depends on the type of light source.

Types of matrix illumination

For TVs and stationary LCD displays today, a direct type of backlight is very often used. This means that the light source (LEDs and lamps) will be located over the entire area of ​​​​the panel. At the same time, two blocks are used to illuminate the LCD matrix in modern devices, each of which consists of two lamps. They are located at the bottom and top of the monitor. As a result, they are placed in such a way as to create a uniform illumination of the LCD matrix. This design allows the backlight to work even in a situation where one of the lamps is out of order. This is where the fun begins, since the inverter is responsible for powering the lamps.

Lamp power inverter

When one lamp stops working, the inverter "sees" that the backlight has lost its uniformity. As a result, the inverter will stop its operation so as not to cause further backlight failure. Thus, it is the inverter that is the reason why, after the failure of one of the 4 lamps, the backlight functions for some time.
Now that we have figured out everything you need to know about the backlight of the monitor, you can start disassembling it and replacing the old-style lamps with LED strip.

Disassembly: step by step instructions

The disassembly of the monitor is as follows:

  • disconnect all loops from the inverter unit and from the monitor controller;

Disconnecting loops

  • unscrew the device with a screwdriver;
  • remove the back panel along with the controller and power supply;

Note! In some places, to remove the back panel, you will need to slightly tuck.

Monitor without back panel

  • we continue to spin the device far. Thus, we get to the matrix (in the figure it is marked with the number 5), the decoder (6) and the light guide with light filters (7);

Monitor Matrix

  • after that, it is necessary to remove the plastic frame around the perimeter. Below it will be two thin films that lie on top of each other. Below them we find a light guide. The photo shows a light filter (8), a polarizing film (9) and a light guide (10);

Matrix Components

  • under the light guide and faulty lamps will be detected;
  • before unscrewing them, it is necessary to pull out the reflective substrate. Although this stage is not needed for every monitor.

When you finally get to the lamps, you can determine the cause of the backlight failure. If the light sources are burned out, then there will be blackening at their ends. Also, the lamp itself could be damaged during mechanical impact.

Installing led: step by step instructions

When you get to the non-working backlight, then your next steps to replace it with an LED strip will look like this:

  • we take out the old lamps from their "grooves";
  • before work, it is imperative to check the hardness of the inverter power supply so as not to get electric shock;
  • To do this, we find a circuit of 12 volts. A couple of electrolytic capacitors are usually placed along the circuit. Next, we track the track going in the direction of the inverter chip and cut it;

Note! De-energizing the inverter must be done.

  • carefully glue the LED strip into these grooves

Gluing the LED strip

  • as a backlight, it is best to take an LED strip that has a neutral white type of glow. In terms of width, it is recommended to use a model with minimum parameters. In addition, it is necessary to select a tape according to such a parameter as the number of LEDs per meter of the product. There must be at least 120 pieces;
  • when the tape was glued, we remove the wires from it and check the entire device for operability. You can power the new LED backlight from the 12 V circuit. In search of such an output, you need to carefully read the conclusions on the board. They must be signed. Also on the board you can find jumpers that have 12 volt power. In them, to power the tape, you just need to solder the wires from the new backlight;

Connecting the ribbon to power in the monitor

  • but here there is a problem in which the backlight will always be on. At the same time, there is no possibility of adjusting the brightness of its glow;
  • to change this situation, it is necessary to find a circuit for adjusting the brightness of the backlight. The "ON" pin will turn on/off the backlight. With the matrix lighting on, approximately 3 volts will be present at this output. Brightness adjusts the "DIM" output. You can adjust the brightness here by changing the duty cycle of the PWM signal. To adjust the brightness, you need to connect the LED strip using an N-channel "field switch". A signal from the “DIM” pin is applied to the gate through a small resistor (100 ... 200 ohms) of this part.

Note! "Polevik" can be taken from an old motherboard.

"Field workers" on the motherboard

On this, we can consider the installation of an LED strip in the monitor to replace old and already unusable lamps can be considered complete. But you need to put all the details together. Remember that after the replacement is completed, you should not have extra parts left. If they remain, it means that you did not return something to its place.
When the monitor is assembled, you need to check the result of your work and evaluate the uniformity of the backlight of the monitor matrix.

If the backlight on the TV works partially, for a short time or does not work at all, then straight arms, a set of screwdrivers, a soldering iron and several meters of LED strip will save the family pet.

Apparently, a few backlights are not working. Over time, they will all rest and the TV can only be used in radio mode. Let's fix the broken lighting. More precisely, change the old CCFL backlight to a modern LED.

Why change CCFL to LED?

In my understanding, CCFL backlighting is a monstrous but fragile monster, which consists of inverters (which give out dangerous voltage), backlights (thin and fragile), powerful metal shields for safety and a bunch of wires. And what exactly broke there - I have no idea. Perhaps the lamps need to be replaced (150 rubles apiece, and there are 16 of them). Maybe the inverter is faulty (it’s hard to find the same one in stock, and the price is more than 1000 rubles apiece). Basically a lottery.

And the LED backlight consists of an LED strip (1000 rubles for five meters), connecting wires (we will find in stocks) and any power source that produces harmless 12V (we will find it on the spot).

Advice for the Thrifty: if you are willing to wait a bit, then buy led strip on aliexpress. It's twice as profitable.

Preparing to replace the backlight

First of all, stock up on screwdrivers of all types and sizes. You will also need a soldering iron and soldering accessories. And it will also take several hours of free time (it took me 6 hours at a leisurely pace). And a lot, a lot free space to lay out all the insides of the TV and not lose anything.

If you are ready, there is nowhere to retreat, read on!

LED Strip for TV Lighting

I bought the most ordinary LED strip in a local store, without bothering with the characteristics, the warmth of the color and other things. I just didn't have any options. More precisely, there were two: either a tape for 60 LEDs (three diodes per 5cm segment), or a tape for 120 LEDs (three diodes for 25mm) - this is one meter. I chose the second one: the gap between the diodes is smaller, and the tape can be cut more accurately in place.

Connected all five meters of the tape to the power source. I found out that the current consumption does not exceed 1A.

Of course, the tape from the store will have all the certificates and parameters carefully indicated on the instructions. The tape will even have a tail for connecting to a power source, it will come in handy.

We disassemble the TV Philips Flat Tv 30pf9975

The back cover is fastened with 16 screws around the perimeter, 6 more are recessed in rather deep wells, 2 more above the main connector block and 1 on the side connector block. A total of 25 star screws.

After removing the cover, we will see this picture.

Here, two massive TV mount beams stand out clearly, they also need to be removed. Near the left beam, a pair of backlight inverters is hidden under a metal cover. Remove the cover, it is on the usual "plus" screws.

We release the inverters from all connectors and carefully remove both boards. I believe the inverters do not heat up sour during operation, so their boards are installed on a thermal pad. The gasket is not adhesive, but voluminous, so the board must be picked up and slowly peeled off from the thermal pad. You can try to poke the gasket with a knife, it will be faster, but it will turn out like this.

It is most convenient to hook the inverter board from the side of the contacts to the backlights, there is no thermal pad there.

Now that the high-voltage dangerous inverters have been removed, we connect the TV to the network, pick up a multimeter and poke into all the contacts in search of the coveted 12V line. It is important that this line only works when the TV is on and does not work in stand-by mode. First, let's check the power outputs of the inverters, of course.

Inverters operate from 24V, that's a bummer. But the sound amplifier board, among other things, receives 12V. We ask from her.

12V is taken from the sound amplifier board. Ground on the black wire (rightmost), +12V on the leftmost pin, or pin 4 from ground. The fourth is easier to solder. Therefore, let's take the connector that was carefully attached to our tape and solder it to the amplifier board. The wire can be clamped between the capacitors on the board.

Before we go all out, let's connect the tape and check if there is enough current from the amplifier to power the entire tape. And is the backlight working properly?

Hooray! The ribbon glows when the TV is on. And it does not glow when it is in stand-by mode. Now it's time to disassemble the TV to the end and replace the CCFL backlight with an LED strip.

We take everything we can. We remove the main fee.

We remove the power supply and the additional power supply board, remove the sound amplifier board.

An additional matrix cable will be found under the power supply. We take it off. The adhesive tape is only there because I already dismantled the TV. We pick up the dark brown holder up and pull out the train.

After that, you can remove the metal casing, under which there is a response backlight board. This board and the connecting cable to the inverters can be thrown away. The casing too.

We continue to disassemble and unscrew until we can pull out the central part with the screen from the TV.

Here we unscrew 14 screws along the edges of the metal frame and remove it.

Now unscrew the screws from the plastic frame. Then we carefully release the matrix loops (having previously removed the metal casing with the board from the back side, it can be seen in the photo in the left upper corner) and remove it.

Be careful with the matrix!

The matrix cannot be bent, so be extremely careful and set it aside on a flat surface.

Under the matrix there will be two thin matte films (do not confuse their order), a plexiglass substrate and ... Backlight!

On the sides, the backlight is in rubber bands, I bit out the wires of the lamps and pulled them out of the rubber bands (because otherwise it’s just soldering). It turned out like this.

Let's try our tape at the installation site.

It turned out 625mm of tape, that is, five meters is enough for exactly 8 segments. Therefore, the segments will be where the plastic holders of the CCFL lamps are now. Take a knife and remove the holders. We also bite out plastic spikes.

Now let's move to the lab. We cut the tape into 8 segments of 625 mm each, lay it with a snake and solder it sequentially. Remember to observe polarity!

After soldering, we carefully check our snake, check the polarity, and only after that we glue the tape in place of the old backlight.

It turned out pretty crooked. However, if you choose between not working at all and working at least somehow, then “it will do.” Now we collect everything in the reverse order. Extra parts will remain from the old backlight: inverters, cables, protective metal casings and fastening screws. And inside the TV will become more spacious, like this.

Please note: I did not shorten the wire going to the backlight. In the future, it will be possible to make a variable resistor on the case and control the brightness. And now the cable is laid in the old fasteners of the inverter loops.

In the near future, a smart-tv board or some kind of raspberry pi can be placed in the place of the inverters, there is enough space here.

We finally assemble the TV, hang it on the wall, connect all the cables and watch. Unlike CCFL lamps, which shine in all directions, LED Strip Light gives a fairly directional light, so on plain background she's barely noticeable.

If I bought an LED strip on aliexpress, I could buy two five-meter skeins for the same 1000 rubles and make 16, not 8 segments. I would have had a more even illumination. But, as I said before, it will do. Just compare with what it was.

LED backlighting is almost invisible against a heterogeneous background, that is, watching TV shows is quite comfortable.

Now about shortcomings. The backlight brightness is not adjustable. But eight segments give an average level of brightness. I plan to add another 5 meters of backlighting to make it more uniform, but ... To be honest, repeating a complete many hours of disassembling the TV is very lazy. Perhaps someday...

And now to the benefits: the TV has lost 1100 grams. Here are all the extra details on the scales.

I successfully sold all these parts at auction. And he saved 10 rubles. But I learned from the buyer that 90% of the problems are in the backlights, that is, it was enough to replace them ... If I knew where to get just such, I would have done so.


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