The TV screen is black but there is sound. What to do if there is sound, but the TV screen does not show? Separate matrix malfunctions

Today we will talk about what to do if there is sound on the LCD TV or plasma, but there is no image. We will also consider self-repair of LCD TVs Samsung, Algy, Philips, Sony and other models, if there is no image and no picture, do it yourself at home

TVs often have such a nuisance - there is sound, there is no image. As a rule, with such a malfunction, the screen does not light up, and everything else works - there is sound, channels switch, DVD works, etc.

Types of breakdowns

If there is sound, but the TV does not show (there is no image), then something may be wrong on the screen:

The screen can become one color;

The image is compressed into a narrow band;

The picture suddenly starts blinking;

The picture is there, but almost invisible;

ripples on the screen.

Why is there sound but no picture?

When there is no picture, but there is sound, most likely the inverter is faulty or there is a problem with the backlights themselves. The screen may go blank due to a malfunction of other components.

When the LCD TV has sound, there is no image, in 90% of cases repair of the power supply or inverter will help.

Of course, the easiest way is to immediately pick up the phone and call a TV repairman. All that is required to tell him is the address, the time of the desired arrival and information about the breakdown. It is also necessary to inform him that there is sound, but there is no image. Do not worry, because you have become an eyewitness to a very common type of malfunction in many LCD TVs and monitors. Although the very statement about the complete absence of the image is not entirely true. There are varieties of failures depending on the degree of damage to the block diagrams. For example, when the picture narrows to a strip (after turning on, or after a malfunction), or when the screen glows white, red, green. Occasionally, such malfunctions provoke ripples on the display, flickering of the color gamut, blurring of brightness, contrast.

The main reason is the lack of backlight, the malfunction of its parts. There are a lot of mechanisms in this TV node, among them backlight lamps, inverters that supply voltage to the lamps, and of course contacts. But there are also special cases in which other broken blocks or TV circuits give failures.

How to fix the problem when there is sound, but no image?

Definitely - repair of the power supply, inverter, backlight lamps, updating contacts. If this does not help, or these parts are intact and serviceable, it is necessary to repair the vertical or line scanner. Such a diagnosis is most likely, because in these cases the screen does not go out 100%, but still shows signs of life. The user can notice this and make a correct conclusion about the breakdown. And if there is a monochromaticity described above (red, green, white screen), it is recommended to repair the video path.

When installing a TV on a liquid crystal screen, like any plasma screen, malfunctions often occur in the matrix, which is often caused by the exhaustion of the resource or the human factor. Strikes on a faulty box only exacerbate the breakdown, as evidenced by the identification of faults where they, in fact, should not be. High-tech plasmas (LCD) are not designed to withstand physical deformation, be careful with such equipment. In case of incompetence, we advise you to refrain from interfering with the holy of holies of technology - the internal component. Call the master to your home, each of them is a specialist in urgent repairs. The advantages of this method of repairing a TV are by no means in a guarantee, not even in the speed and quality of the work carried out, but first of all in accessibility. The services of professionals are aimed at helping people at a democratic, affordable price. They are getting rid of unnecessary work, a headache for owners of broken models.

The inverter in the TV is a device for starting and stable operation of the fluorescent lamps for backlighting the LCD panel. Provides a constant glow of these light sources for a long time and effectively controls their brightness. It can be made in the form of one or two separate blocks (master / slave), and also located together with the power supply on a single board. When self-repairing a television receiver inverter, you need to know the functions that it performs.

The tasks of the television inverter:

O conversion of direct voltage 12 - 24 volts to high-voltage alternating

O stabilization and adjustment of lamp current

O Backlight brightness adjustment

O Providing protection against overloads and short circuits

Wiring diagram of a simple inverter for 2 backlight lamps

The device is implemented on a PWM controller U1 (OZ960), two assemblies of field-effect transistor switches (u1, u2) and high-voltage transformers T1, T2. The CN1 connector supplies 12 volt power (F1), an ON/OFF command, and a constant voltage (Dimm) for dimming. The protection node (D2, D4, D5, D6) analyzes the current or voltage at the output of the device and generates overload and feedback voltages (OS) supplied to the PWM. If one of these voltages exceeds the threshold value, the oscillator is blocked on U1, and the inverter will be in the protection state. The node is blocked when the supply voltage is low, when the supply voltage "drops" at the moment the load is turned on, when the converter is overloaded or short circuited.

Common Inverter Fault Symptoms

Lights do not turn on

Backlights turn on briefly and then turn off

Unstable brightness and screen flickering

Inverter intermittently does not turn on after a long period of inactivity

Irregular illumination of the screen with a 2-inverter circuit

Features of the repair of the inverter unit

When diagnosing faults related to the correct operation of the inverter, you should first of all make sure that there are no ripples in the supply voltage and its stability. Pay attention to the passage of startup commands and backlight brightness control from the motherboard. Eliminate the influence of backlights by using their equivalent in cases where the problem is not clear. Take the opportunity to remove the protection from the inverter during the repair to determine the defective part. Do not forget about a careful visual inspection of the board and what every professional TV technician uses when repairing TVs at home - measuring voltage, resistance, capacitance using special instruments or a tester.

Sometimes, upon closer inspection of the board, you can see "burnt" parts that need to be replaced. Field-effect transistor keys often fail, but sometimes their replacement does not always lead to a positive result. The unit may recover for an indefinite time, and then the malfunction may occur again. You have eliminated the effect, but not the cause. Therefore, without knowing the intricacies of repairing these devices, you can lose a lot of time and effort to restore them. And, if there is any doubt about the success of the case, call the master, who has already repaired such devices many times and knows all the "pitfalls and shoals" thanks to his accumulated experience and professional knowledge.

High-voltage transformers are considered a weak link in the composition of inverter units. Operation under high voltage conditions requires special build quality of these components and places high demands on the insulation properties. In addition, it should be said that the transformers can noticeably heat up during the operation of the backlight. Defects such as an open or interturn circuit of the windings of these parts are common. The diagnostics of these elements can be difficult because a short circuit or an open circuit can only be observed in the operating mode, and their “diagnosis” in a de-energized state will not reveal problems with them. Here, changing places of a dubious and serviceable transformer and further analysis of the situation can come to the rescue.

Different TVs use inverters with different numbers of transformers. In small-sized devices, 2-4 transformers can be installed in the inverter, in TVs of large diagonals, especially of previous years of production, there were up to 20 of the same type of products. Naturally, a large number of them reduces the reliability of the circuit as a whole, therefore, in modern models, their use is minimized through innovative technical solutions.

A symptom of an inverter malfunction in most cases is the absence of an image on the TV screen when there is sound. However, situations are possible when the TV, after trying to turn on, goes back into standby mode or starts flashing the LEDs on the front panel, and no sound appears in this case. The nature of the defect is different, and the source can be the same inverter unit. In some TV models, there is a feedback signal from the inverter to the motherboard processor, indicating a malfunction in its operation. Not having received confirmation from the inverter that everything is in order with it, the processor changes the TV operating mode to standby or displays error messages through the LED indicators. For some manufacturers, after a certain number of unsuccessful starts, the system may stop giving the command to turn on the backlight until the errors are reset or the memory is cleared.

TYPICAL FAULTS ASSOCIATED WITH THE BACKLIGHT.
The matrix is ​​the most expensive part, and before opening the matrix and looking at the lamp, it is necessary to determine the malfunction of the backlight, and for this you need to make sure of this by connecting the matrix to a pre-serviceable backlight module, or connect a pre-serviceable backlight instead of your matrix . Malfunctions of backlight modules and so on will be discussed later.
A malfunction of the backlight lamp is often easy to determine visually, pink or closer to red background of the matrix or dimming along the edges of the matrix is ​​a prerequisite for the fact that the backlight lamp or high-voltage converter (matrix backlight module) will soon die in your matrix due to increased load currents. Lamp failure can be of two types, mechanical or cathode burnout.
In the first case, we have mechanical pressure on the matrix (kink, impact, fall) and, as a result, a broken backlight. In this case, when disassembling the matrix, you must be especially careful, because. it is possible for fragments to get inside the matrix filters, which can cause damage to the filters and reflectors.

REPLACING THE BACKLIGHT LAMP.

Replacing the backlight lamp is a procedure at first glance that is not complicated and not long, but we will analyze it all in more detail.
To replace the lamp, you need: Experience in this work, knowledge of the matrix structure, a clean and dust-free workplace, or a special mechanical device. Matrices were repeatedly brought to me, after an unqualified replacement of the lamp, and in 60% the matrix was only subject to replacement, in other cases, repairing damage cost more than a regular lamp replacement.

According to the manufacturers, the matrix illumination lamp is an element of the matrix design and must be replaced together with the matrix, i.e. The matrix manufacturer does not provide for replacement of the lamp in non-production conditions. The backlight is installed inside the reflective container and glued to the refractive and other filters and screen reflectors. Attempting to pull out the lamp may cause damage to the filter stack, or the filters themselves and the image quality of the matrix will deteriorate greatly. When replacing the backlight, inexperienced people often damage the cables connecting the glass to the decoder, which will damage the matrix

The inverter is a complex electronic device, the self-repair of which can cause certain difficulties. These blocks for TVs with diagonals from 26 inches and above are "tied" to a specific LCD panel and, according to manufacturers, are a single device (together with the T-con block). It is very rare to find electronic circuits for these products, and never for a matrix controller. Therefore, even a professional, when diagnosing this equipment, has to remember the experience of repairing similar devices, be guided by the general principles of their circuit solutions and use the database of datasheets for backlight driver microcircuits and key transistors.

Among the typical defects that fall into this category, one can note the failure of the BD9897FS PWM controller chip in Philips TVs made on Master and Slave inverters, open or burnout light-emitting diodes in the backlight bars of Samsung UE32F50XX series TVs, turn-to-turn short circuit or open circuit of inverter transformers in all models of television LCD receivers. It should be mentioned that there are a large number of types of TVs from different manufacturers, in which the correct operation of the backlight unit is monitored by the central processor, and if this node fails, an error signal arrives on the motherboard, blocking the operation of the entire device or putting it into self-diagnosis mode. Visually, this is displayed by flashes of the emitting diode on the front panel. The sound channel in this mode is blocked by the processor.

The high standard of quality in TV production that has become the norm in recent times is not a panacea for the failures, problems and defects that sometimes occur in any electronics. Needless to say, if the users themselves rarely read the accompanying instructions for TVs, not to mention the observance of operating conditions. The Soviet past has taught many to self-repair, hitting the box in order to "improve the quality of work." But this is fundamentally wrong, because today the manufactured products are technologically advanced, quite sensitive to any mechanical influences, so even one inept intervention in the case or a blow to it can create a lot of trouble for the owner. One of the existing signs of a human factor, as a rule, or a power surge in the network, is the lack of sound for the video. The power supply of a modern TV, whether it is a plasma panel or LCD, LED TV, is a switching power supply with a given range of output supply voltages and a rated power delivered to the load for each of them. The power board can be made as a separate unit, which is typical for receivers with small diagonals, or integrated into the television chassis and located inside the device.

Typical symptoms of a malfunction of this unit are as follows:

The TV does not turn on when the power button is pressed

The standby LED is on, but there is no transition to the operating mode

Noise in the image in the form of kinks and stripes, background sound

There is sound, but no image, which may appear after a while

Requires several attempts to turn on for the appearance of a normal picture and sound

Let's analyze the circuitry of a standard power supply and its typical malfunctions using the ViewSonic N3260W TV as an example.

To fully view the diagram, you can open it in a new window and enlarge it, or download it to your computer or mobile device

The first thing to start with is a thorough visual inspection of the board on the device turned off from the network. To do this, the unit must be removed from the TV by disconnecting the connectors, and it is imperative to discharge the high-voltage capacitor in the filter - C1. In the blocks of this series of TVs, the electrolytic capacitors of the filters of the secondary power supplies often fail. They are easily diagnosed by the swollen top cover. All capacitors, the appearance of which is in doubt, must be replaced immediately.

The standby unit is made on IC2 (TEA1532A) and Q4 (04N70BF) with 5V output voltage stabilization elements on the IC7 optocoupler and the ICS3 EA1 controlled zener diode. The missing or underestimated voltage at the output of this node, measured on capacitors CS22, CS28, indicates its incorrect operation. The experience of restoring this section of the circuit indicates that the most vulnerable elements are IC2, Q7, ZD4 and Q11, R64, R65, R67, which require verification and replacement if necessary. The operability of the parts is checked by the tester directly on the unit board. At the same time, questionable components are soldered and tested separately, in order to exclude the influence of neighboring circuit elements on their performance. IC2 is simply replaceable.

If there is a 5V voltage output at the output of the standby mode circuit, a red LED lights up on the front panel of the TV. On command from the remote control or a button on the front panel of the TV, the power supply must switch to operating mode. This command - Power_ON - in the form of a high potential of about 5V comes to 1 pin of the CNS1 connector, opening the keys on QS4 and Q11. At the same time, supply voltages are applied to the IC3 and IC1 microcircuits, transferring them to the operating mode. To pin 8 of IC3 directly from the collector of Q11, to pin 12 of IC1 through the Q9 switch after starting the PFC circuit. The performance of the Power Factor Correction circuit is indirectly determined by the increase in voltage from 310 to 390 volts measured across capacitor C1. If the output supply voltages of 12V and 24V appear, then the main source on IC3, Q1, Q2 is functioning normally. Practice shows the low reliability of the UCC28051 and LD6598D in critical conditions, when the filtering of secondary sources deteriorates, and their replacement is of an ordinary nature.

Summarizing the experience of repairing television power supplies, it should be noted that the weakest link in their composition is the filter capacitors, which lose their properties and nominal parameters over time. Sometimes a faulty "capacity" is visible by a swollen lid, sometimes not. The consequences of poor filtering of the rectified voltage can be very different: from the loss of performance of the power source itself, to damage to the elements of the inverter or software failure in the memory chips on the motherboard.
Diagnostics and repair of T-con

Diagnosing a malfunction in a timing controller can sometimes be extremely difficult. The fact is that the connection of this block with the main board and the LCD matrix is ​​so great that it is sometimes not possible to visually determine what is the source of the defect. Only measurements at the T-con control points can indirectly indicate its inoperability. When repairing the matrix controller yourself, you must have a large amount of information that, with a careful and painstaking search, the Internet can provide. The controller itself is considered an integral part of the LCD panel, and manufacturers do not provide wiring diagrams for this unit. This situation makes the telemaster, when repairing this unit, be guided primarily by his professional instinct and experience in such repairs.

If your TV began to show a low-contrast, negative, whitish image with moiré patterns of various shades in the light or dark areas of the picture, it is likely that the matrix controller unit is not working correctly. To exclude the influence of the motherboard and to carry out diagnostics, many manufacturers of LCD matrices provide for the inclusion of T-con in offline mode. In this case, the cable connecting these boards is removed, only the supply voltage is supplied to the controller, and by closing the service contacts, the panel is put into test mode. When the LCD panel is in good condition and the timing of the controller, the self-diagnosis of the panel is observed on the screen in the form of alternating colored fields and stripes, as from a test television signal generator. Each name of the LCD panel has its own method of entering the test mode.

To eliminate the influence of the LCD panel on the matrix controller when measuring the supply voltage of the drivers or the reference voltages for the DAC drivers, a short-term disconnection of the loops, one or two, on the LCD panel is used. By the nature of the change in instrument readings and the visual perception of the image on the screen, certain conclusions can be drawn about the causes of the malfunction. For reliable control of the unit's performance during measurements, it is necessary to control the presence, shape, amplitude, frequency and duty cycle of pulses, which can be carried out using an oscilloscope. The presence of an oscilloscope facilitates the search for a defect and is always used for diagnostics in a stationary service center.

In some cases, it is necessary to doubt the health of the matrix controller in the absence of an image with a dark or very light (white) monitor screen. It is necessary to control the passage of the supply voltage from the main board and the formation of secondary voltages by DC / DC converters in the block itself. Sometimes problems with the timing controller, and even with the matrix itself, can arise due to the fault of the owner who is too careful, wiping the TV screen with a too damp cloth, or, conversely, careless, spilling liquid on the LCD panel or inside the device. If moisture gets on the matrix, irreparable consequences can occur in the form of destruction of conductive loops, their corrosion, shorting of drivers and failure of the matrix controller due to a critical violation of its operation mode.

Repair of the timing controller is not provided by the manufacturer of LCD matrices, only its replacement. Therefore, technical information on the restoration of the block is not provided and there are no diagrams for it. However, in our workshop, every opportunity is used to repair the TV at the component level without replacing blocks and boards. When restoring, technical information is used in the form of "datasheets" - descriptions, characteristics, connection diagrams of the components that make up the controller, which allows the telemaster to successfully carry out repair work on such a complex unit of a modern TV as T-con.

As in the investigation of crimes, in our case it is important to establish everything to the smallest detail: how did the malfunction occur, what preceded it, what is the nature of its manifestation? This information will be needed by a specialist to accurately localize the source of all troubles in TV. Also, this is important when carrying out self-repair of the TV. First, you should accurately determine the "broken" part. As practice shows, in 80% of cases the sound on the TV disappeared due to three types of malfunctions. Let's look at each of them in detail. The first is caused by failures in the operation of the radio channel, damage to the effects processor, the entire mechanism of the central processor is possible, and occasionally there are failures in memory processing. The second is a malfunction of the speaker, which is caused by wear, contact separation, burnout. The third is the breakdown of microcircuits, and there are quite a few factors preceding this, starting with network outages, power surges, and ending with a short circuit, failure of capacitors or, again, contacts.

But back to the topic of the article and begin to act. Our first priority is to restore the sound on the TV, the source is approximately installed, which means it's time to repair. We unscrew the case with tools and carefully remove it without touching the rest of the blocks. We look at the details and visually look for potential breakdowns. If they are not there, we proceed to check the operability of the circuits and blocks, in the absence of responses, we pay attention to the contacts, even if they are connected, they can be “cold”, which means the circuit itself is not working. When such situations are detected, we change the scheme or try to debug it

The reasons that there is sound on the Samsung TV, but there is no image, can be software and hardware failures. Why do such breakdowns occur? Power surges, mechanical damage, improperly installed applications or updates - all this can lead to incorrect TV operation.

If the TV has stopped working, this does not mean that you need to contact the service center. Some problems can be fixed on your own. Now we will analyze the main reasons for the appearance of problems with the image, and also study ways to eliminate the failure that has occurred.

On the LCD TV screen, image problems can manifest themselves in several ways. The sign is of great importance. Because the causes of the malfunction are determined according to the symptom.

Mostly there is no image on the screen in principle, but the sound is present. However, there are other situations as well:

• the picture flickers, ripples appear;
• the video signal periodically disappears, and then reappears;
• vertical stripes;
• some elements of the LED backlight are flashing;
• there is an image, but there are defects - stripes or squares;
• the outline of the picture is green or red;
• vertical colored stripes on the screen;
• viewing is not possible because the picture is blocked by various interference.

There are a lot of reasons why the image on the TV disappeared. It is not always possible for users to independently determine the cause of a malfunctioning TV. Therefore, in order to fix the breakdown, sometimes you have to contact service centers.

Image problems appear on both plasma and LCD models. The manufacturer should not be blamed either. The defects listed above are manifested not only in the operation of Samsung TV. Owners of devices from other manufacturers also face similar problems.

Sometimes the TV turns on and even a splash screen appears, but then the display goes blank. The sound is present, and the channels are switched using the remote control. The main reasons for this failure are:

• the inverter that supplies voltage to the elements of the LED backlight is faulty;
• the presence of violations in the operation of the convector, loop or even decoder;
• mechanical damage to the matrix, motherboard or backlight element;
• problems with electrolytes that are in the power supply;
• broken electrolytic capacitor;
• the matrix cable, which provides connection to the board, has departed.

Breakage of any loop can lead to such a malfunction. To definitely determine the cause of the incorrect operation of the TV, you need to seek help from specialists.

In older TVs (CRT models), such defects appeared due to problems with vertical or horizontal scanning.

What problems can be fixed by yourself

1. Check the integrity of the connecting cable. If the wire is broken or damaged, replace it with a new one.
2. Increase the volume to the maximum, after that the black screen may disappear and the TV will start working in the usual mode.

3. On the rear panel, check the quality of the connection of the antenna cable to the appropriate socket. The plug may be damaged.

4. Check the TV settings, it is possible that the image disappears due to incorrectly set parameters. Return to default settings.

The above recommendations are relevant only if the screen is in working order. How to check it? Turn on the TV, if the splash screen appears immediately after startup and then disappears, then the problem lies in the wrong settings or connection (in this case, a lot depends on the signal source). Users will be able to eliminate such problems on their own.

Blue screen, white screen and all sorts of other malfunctions can also appear due to faulty hardware modules that burn out due to short circuits. To prevent such breakdowns, get an uninterruptible power supply.

If, after turning on the Smart TV, the picture disappears and the sound disappears, then first of all you need to check the performance of the wire. This can be done using the Moninfo program. The software is designed to check the quality of the transmission of various signals (audio, video).

If the software detects irregularities, then the problem is with the connecting cable. To check the quality of the video signal, follow the simple step-by-step instructions:

1. On the remote control, press the button with the icon in the form of a house.
2. Go to the settings menu.
3. Choose a section "Support" and then tab "Self-diagnosis".
4. Activate the team "Run image test".
5. After the diagnostics is completed, a list of recommendations from Samsung will appear, use them.

We will also consider other problems, as well as analyze ways to eliminate them.

Almost all types of problems can be fixed independently at home. Without the use of professional equipment. It is much more difficult with hardware breakdowns, because in order to replace a broken part, you need to disassemble the TV.

When to Call a Service Center

Self-repair is limited to fixing software failures and cable-related problems. Complex hardware failures, due to which there is no image on the Samsung TV, it is more expedient to entrust the masters of the service center.

The most common failure is a malfunction of the inverter. This module provides voltage to the lamp, it also regulates the start of the backlight. The investor is presented in the form of one or more blocks of microcircuits. It all depends on the TV model. The accessory is located next to the power supply.

Before proceeding with the repair, experts check the presence of incoming voltage. Pulsations should be absent. After this, the wizard is watching how the command goes to start the lamps from the motherboard. Mostly the failure occurs at this stage.

If no damage is found, the backlight elements are replaced. Re-testing is underway. If the system works properly, the repair is completed.

Sometimes the problem does not disappear after replacing the lamps, which means that the problem is much more serious than it initially seemed. First, a visual inspection is carried out. Experts are trying to determine the presence of burnt links.

Quite often, field-effect transistor switches break down, but replacing them may not give a result or will solve the problem for a short period of time. The fact is that replacing the keys eliminates the consequence of the malfunction, and not its cause. Therefore, the defect occurs repeatedly during the subsequent operation of the TV.

Another weak point of inverters are high voltage transformers. These elements are heavily loaded. Accordingly, natural wear occurs extremely quickly. Replacing the transformers also solves the problem.

The second type of hardware failure is backlight lamps. Engineers simply replace defective lamps with original components. The absence of an image may be the result of cathode burnout. This problem is fixed as follows. The bolts fixing the board are unscrewed. The matrix is ​​not opened, since the masters use a special tool that allows you to turn off the component. Dust will not get inside the matrix.

Manufacturers of TV devices claim that the lamps must be replaced exclusively with the matrix. Turning off the lamp is carried out as carefully as possible. Basically, the part is glued to other elements of the system. High temperature causes the lamp to be soldered to the chip.

The cable that connects the lamp to the board is disconnected, and only then the component is removed. The new lamp is fixed in the same way.

Burnout of the power board is another reason that there is sound, but there is no image. This component has several forms, it all depends on the size of the TV device. For example, compact models are equipped with boards in the form of a block. Large TVs are equipped with a board in the form of a chassis. The service center masters will quickly disassemble the TV, and then change the faulty elements.

The weak point of any power board is the filter capacitors. When the damaged elements are replaced, the power supply, lamps and inverter are connected.

Hardware repair is indeed a very expensive procedure, but trying to change the inverter, lamps or power board yourself will lead to an aggravation of the malfunction. Therefore, it is better to contact the service center.

Below is a drawing of the inverter. Simplified, but it's easy to understand why the TV does not show, fix the problem. What kind of beast is the inverter, how to deal with it? Let's answer the question, learn something new about modern technologies. The topic is close to welders, similar methods are used to ignite the electrode. The advantage is adjustability. The pulse-width modulator easily changes the operating voltage of the primary winding of the transformer by varying the current. The increased frequency is used to reduce the size. On ultrasound, the transformer takes up much less space.

Inverter switching circuit

The operation of a modern TV

There is sound, there is no picture - the breakdown concerns the imaging circuits. The scan is capable of failing, but in most cases the matter is explained as follows. Previously, a ray tube dominated television, paid triple attention to the posistor, today LCD monitors cannot do without backlighting. Moreover, the quality / price of the device mainly depends on this. Various techniques are used for illumination, more often ordinary halogen lamps covering the perimeter or part. Organic diodes are not affordable for everyone. Lamps for ignition, combustion require the creation of a discharge. The process of ionization of gases is impossible without high voltage. How to get in a miniature (comparatively) device?

Correct Answer: Transformer To get a thousand volts out of twelve, look for a large transformer ... Therefore, a pulse generator controlled by a pulse-width modulator is used. In other words, a key, an inverter. Clocked in the circuits cuts the signal, in our case it forms the required slope of the pulses so that the transformer can easily pass. Depending on the width of the pulses, the signal power changes. This is how the current is regulated:

The question arises: why do we need an inverter if the pulse-width modulator could control the transformer itself? related to load capacity. The microcircuit detects a certain limit of power dissipation. A series of microcircuits are trying to be hidden in the same case, achieving uniformity. It is permissible to combine an inverter and a pulse-width modulator in one circuit, they do it infrequently, the current consumption of the assembly will increase. Consequently, the power dissipation will increase. Will lead to a violation of uniformity.

The inverter is a simple circuit, often on one key element. Therefore, with the help of it it is easy to obtain a significant output current without loss of uniformity. The enable key is usually formed by semiconductor transistors. The power reaches the dimmer, whose voltage level controls the pulse-width modulator. More pulse width, brighter image. The incoming lower branch (see figure) repeats the shape of the signal, controlling the winding of the transformer. The secondary circuit generates current. The backlight lamps light up.

The feedback current is compared with the comparator dimmer signal, which is part of the pulse-width modulator. In case of mismatch, the duration of the pulses is adjusted in the desired direction. That's the whole inverter. Familiar to welders, converts DC to AC voltage by controlling signal parameters. The voltage rises, welders need a significant arc current.

TV inverter repair

It happens that the TV screen does not show, there is sound. In most cases, the snag concerns the backlight lamps, the inverter. It is logical to start testing from here. Due to the design features, it is difficult to get to the backlight lamps; troubleshooting begins with an electrical circuit. inverter. Find by the presence of a transformer on the board, do not confuse it with the power supply (where the TV cord goes).

The input should be 12 volts, measure the value with a tester, check the integrity of the fuse. If you get burned, wait a while to rejoice, it usually means that something has broken inside. After applying 12 volts, start the test with power on the dimmer circuit. Without it, the screen will refuse to glow. Zero voltage - the transistor switch is to blame. Fix by replacing burnt parts. The transistors are ringing for a short circuit.

The permission signal is called Enable, it is supplied by the TV's electronic board. Unplug the connector, apply 12 volts to power and 5 volts to Enable. The lamps lit up - the TV board is faulty. Otherwise, we continue the search. It is time to conduct an external inspection of the capacitors, transformer, lamp connectors. Faulty parts are easy to distinguish:

• Resistors turn black.
• The protective film melts on transformers.

If, after starting the circuit, a voltage surge appears on the lamp, it is necessary to clean the contacts. It is useful to try to insert the correct ones. There is a high probability that the backlight will work again. It happens that the lamps blink after turning on, immediately go out. Indirectly indicates a fault in the feedback circuit, or overload.

You should check the capacitors in the branches of the lamp, ring the transformer windings (zero resistance indicates a short circuit), then check the elements along the feedback circuit. Transistors, capacitors, diodes, resistors, etc. It is important to know the features of the operation of various microcircuits; technical sheets usually indicate the permissible modes. It often helps to identify a malfunction in the form of a conventional circuit. Some elements do not pull the load, create the wrong conditions.

The behavior described above, when the lamps, having flashed, go out, is characteristic of the disruption of the oscillations of the pulse-width modulator. Nothing at the output of the transformer. If you find a frequency measuring device, connect a 100 kΩ resistor to the lamp connector. Oscillations of ultrasound and higher (tens of kHz) should be recorded. Depending on the brightness settings, the frequency changes: it increases with increasing.

The measured parameters do not correspond to the ratings - the primary winding voltage generation circuit is to blame. After the inverter, there are several signal filtering / optimizing elements. Chokes, transistors, resistors. Checked in the usual order for serviceability. With unstable brightness, blinking, suspicion concerns the central circuit of the TV, or the pulse-width modulator.

Lost TV settings

It happens that the channel setup has gone wrong. The TV's memory chip is in no way related to the backlight. In this case, there are ripples on the screen, there is no sound. The TV is slow to show channels, you should check the promotions of the provider. Watch www.youtube.com/watch?v=YtqrIVaEDNI#t=11. The video says: without updating the software, Tricolor TV channels will refuse to be caught. The problem is easily fixed by following the steps below.

Broadcasting is carried out in the DBV-T2 format - the channels are divided into multiplexes. One frequency transmits many programs, the TV, using the built-in adapter, selects information broken by frames, converting it into a form that is digestible for the screen. The multiplex setting is lost, all channels included in the composition disappear. You need to know the broadcast frequency. Corresponds to the digital television channel number. After you need to visit the TV menu, start searching for channels at the selected frequency. Upon completion of the operation, a list of caught stations, signal level, quality should appear on the screen.

Sometimes the antenna is to blame. In our area, the cable is cut very often, especially satellite. And not at all with the aim of handing over to the collection point for non-ferrous metals, considerations of competition. The action is very difficult to track and punish. From time to time, local providers try to crush the "heavenly" ones broadcasting via satellite. Trite to check the quality of the connection. In the event of a break, the receiver will not see the converter or disc.

We hope we answered the question why the TV does not show, what could break, how to fix the attack. Now readers themselves will be able to find the problem. Please note that the backlight should be removed as carefully as possible so as not to damage.

Today we will talk about what to do if there is sound on the LCD TV or plasma, but there is no image. We will also consider self-repair of LCD TVs Samsung, Algy, Philips, Sony and other models, if there is no image and no picture, do it yourself at home

TVs often have such a nuisance - there is sound, there is no image. As a rule, with such a malfunction, the screen does not light up, and everything else works - there is sound, channels switch, DVD works, etc.

Types of breakdowns

If there is sound, but the TV does not show (there is no image), then something may be wrong on the screen:

The screen can become one color;

The image is compressed into a narrow band;

The picture suddenly starts blinking;

The picture is there, but almost invisible;

ripples on the screen.

Why is there sound but no picture?

When there is no picture, but there is sound, most likely the inverter is faulty or there is a problem with the backlights themselves. The screen may go blank due to a malfunction of other components.

When the LCD TV has sound, there is no image, in 90% of cases repair of the power supply or inverter will help.

Of course, the easiest way is to immediately pick up the phone and call a TV repairman. All that is required to tell him is the address, the time of the desired arrival and information about the breakdown. It is also necessary to inform him that there is sound, but there is no image. Do not worry, because you have become an eyewitness to a very common type of malfunction in many LCD TVs and monitors. Although the very statement about the complete absence of the image is not entirely true. There are varieties of failures depending on the degree of damage to the block diagrams. For example, when the picture narrows to a strip (after turning on, or after a malfunction), or when the screen glows white, red, green. Occasionally, such malfunctions provoke ripples on the display, flickering of the color gamut, blurring of brightness, contrast.

The main reason is the lack of backlight, the malfunction of its parts. There are a lot of mechanisms in this TV node, among them backlight lamps, inverters that supply voltage to the lamps, and of course contacts. But there are also special cases in which other broken blocks or TV circuits give failures.

How to fix the problem when there is sound, but no image?

Definitely - repair of the power supply, inverter, backlight lamps, updating contacts. If this does not help, or these parts are intact and serviceable, it is necessary to repair the vertical or line scanner. Such a diagnosis is most likely, because in these cases the screen does not go out 100%, but still shows signs of life. The user can notice this and make a correct conclusion about the breakdown. And if there is a monochromaticity described above (red, green, white screen), it is recommended to repair the video path.

When installing a TV on a liquid crystal screen, like any plasma screen, malfunctions often occur in the matrix, which is often caused by the exhaustion of the resource or the human factor. Strikes on a faulty box only exacerbate the breakdown, as evidenced by the identification of faults where they, in fact, should not be. High-tech plasmas (LCD) are not designed to withstand physical deformation, be careful with such equipment. In case of incompetence, we advise you to refrain from interfering with the holy of holies of technology - the internal component. Call the master to your home, each of them is a specialist in urgent repairs. The advantages of this method of repairing a TV are by no means in a guarantee, not even in the speed and quality of the work carried out, but first of all in accessibility. The services of professionals are aimed at helping people at a democratic, affordable price. They are getting rid of unnecessary work, a headache for owners of broken models.

The inverter in the TV is a device for starting and stable operation of the fluorescent lamps for backlighting the LCD panel. Provides a constant glow of these light sources for a long time and effectively controls their brightness. It can be made in the form of one or two separate blocks (master / slave), and also located together with the power supply on a single board. When self-repairing a television receiver inverter, you need to know the functions that it performs.

The tasks of the television inverter:

O conversion of direct voltage 12 - 24 volts to high-voltage alternating

O stabilization and adjustment of lamp current

O Backlight brightness adjustment

O Providing protection against overloads and short circuits

Wiring diagram of a simple inverter for 2 backlight lamps

The device is implemented on a PWM controller U1 (OZ960), two assemblies of field-effect transistor switches (u1, u2) and high-voltage transformers T1, T2. The CN1 connector supplies 12 volt power (F1), an ON/OFF command, and a constant voltage (Dimm) for dimming. The protection node (D2, D4, D5, D6) analyzes the current or voltage at the output of the device and generates overload and feedback voltages (OS) supplied to the PWM. If one of these voltages exceeds the threshold value, the oscillator is blocked on U1, and the inverter will be in the protection state. The node is blocked when the supply voltage is low, when the supply voltage "drops" at the moment the load is turned on, when the converter is overloaded or short circuited.

Common Inverter Fault Symptoms

Lights do not turn on

Backlights turn on briefly and then turn off

Unstable brightness and screen flickering

Inverter intermittently does not turn on after a long period of inactivity

Irregular illumination of the screen with a 2-inverter circuit

Features of the repair of the inverter unit

When diagnosing faults related to the correct operation of the inverter, you should first of all make sure that there are no ripples in the supply voltage and its stability. Pay attention to the passage of startup commands and backlight brightness control from the motherboard. Eliminate the influence of backlights by using their equivalent in cases where the problem is not clear. Take the opportunity to remove the protection from the inverter during the repair to determine the defective part. Do not forget about a careful visual inspection of the board and what every professional TV technician uses when repairing TVs at home - measuring voltage, resistance, capacitance using special instruments or a tester.

Sometimes, upon closer inspection of the board, you can see "burnt" parts that need to be replaced. Field-effect transistor keys often fail, but sometimes their replacement does not always lead to a positive result. The unit may recover for an indefinite time, and then the malfunction may occur again. You have eliminated the effect, but not the cause. Therefore, without knowing the intricacies of repairing these devices, you can lose a lot of time and effort to restore them. And, if there is any doubt about the success of the case, call the master, who has already repaired such devices many times and knows all the "pitfalls and shoals" thanks to his accumulated experience and professional knowledge.

High-voltage transformers are considered a weak link in the composition of inverter units. Operation under high voltage conditions requires special build quality of these components and places high demands on the insulation properties. In addition, it should be said that the transformers can noticeably heat up during the operation of the backlight. Defects such as an open or interturn circuit of the windings of these parts are common. The diagnostics of these elements can be difficult because a short circuit or an open circuit can only be observed in the operating mode, and their “diagnosis” in a de-energized state will not reveal problems with them. Here, changing places of a dubious and serviceable transformer and further analysis of the situation can come to the rescue.

Different TVs use inverters with different numbers of transformers. In small-sized devices, 2-4 transformers can be installed in the inverter, in TVs of large diagonals, especially of previous years of production, there were up to 20 of the same type of products. Naturally, a large number of them reduces the reliability of the circuit as a whole, therefore, in modern models, their use is minimized through innovative technical solutions.

A symptom of an inverter malfunction in most cases is the absence of an image on the TV screen when there is sound. However, situations are possible when the TV, after trying to turn on, goes back into standby mode or starts flashing the LEDs on the front panel, and no sound appears in this case. The nature of the defect is different, and the source can be the same inverter unit. In some TV models, there is a feedback signal from the inverter to the motherboard processor, indicating a malfunction in its operation. Not having received confirmation from the inverter that everything is in order with it, the processor changes the TV operating mode to standby or displays error messages through the LED indicators. For some manufacturers, after a certain number of unsuccessful starts, the system may stop giving the command to turn on the backlight until the errors are reset or the memory is cleared.

TYPICAL FAULTS ASSOCIATED WITH THE BACKLIGHT.
The matrix is ​​the most expensive part, and before opening the matrix and looking at the lamp, it is necessary to determine the malfunction of the backlight, and for this you need to make sure of this by connecting the matrix to a pre-serviceable backlight module, or connect a pre-serviceable backlight instead of your matrix . Malfunctions of backlight modules and so on will be discussed later.
A malfunction of the backlight lamp is often easy to determine visually, pink or closer to red background of the matrix or dimming along the edges of the matrix is ​​a prerequisite for the fact that the backlight lamp or high-voltage converter (matrix backlight module) will soon die in your matrix due to increased load currents. Lamp failure can be of two types, mechanical or cathode burnout.
In the first case, we have mechanical pressure on the matrix (kink, impact, fall) and, as a result, a broken backlight. In this case, when disassembling the matrix, you must be especially careful, because. it is possible for fragments to get inside the matrix filters, which can cause damage to the filters and reflectors.

REPLACING THE BACKLIGHT LAMP.

Replacing the backlight lamp is a procedure at first glance that is not complicated and not long, but we will analyze it all in more detail.
To replace the lamp, you need: Experience in this work, knowledge of the matrix structure, a clean and dust-free workplace, or a special mechanical device. Matrices were repeatedly brought to me, after an unqualified replacement of the lamp, and in 60% the matrix was only subject to replacement, in other cases, repairing damage cost more than a regular lamp replacement.

According to the manufacturers, the matrix illumination lamp is an element of the matrix design and must be replaced together with the matrix, i.e. The matrix manufacturer does not provide for replacement of the lamp in non-production conditions. The backlight is installed inside the reflective container and glued to the refractive and other filters and screen reflectors. Attempting to pull out the lamp may cause damage to the filter stack, or the filters themselves and the image quality of the matrix will deteriorate greatly. When replacing the backlight, inexperienced people often damage the cables connecting the glass to the decoder, which will damage the matrix

The inverter is a complex electronic device, the self-repair of which can cause certain difficulties. These blocks for TVs with diagonals from 26 inches and above are "tied" to a specific LCD panel and, according to manufacturers, are a single device (together with the T-con block). It is very rare to find electronic circuits for these products, and never for a matrix controller. Therefore, even a professional, when diagnosing this equipment, has to remember the experience of repairing similar devices, be guided by the general principles of their circuit solutions and use the database of datasheets for backlight driver microcircuits and key transistors.

Among the typical defects that fall into this category, one can note the failure of the BD9897FS PWM controller chip in Philips TVs made on Master and Slave inverters, open or burnout light-emitting diodes in the backlight bars of Samsung UE32F50XX series TVs, turn-to-turn short circuit or open circuit of inverter transformers in all models of television LCD receivers. It should be mentioned that there are a large number of types of TVs from different manufacturers, in which the correct operation of the backlight unit is monitored by the central processor, and if this node fails, an error signal arrives on the motherboard, blocking the operation of the entire device or putting it into self-diagnosis mode. Visually, this is displayed by flashes of the emitting diode on the front panel. The sound channel in this mode is blocked by the processor.

The high standard of quality in TV production that has become the norm in recent times is not a panacea for the failures, problems and defects that sometimes occur in any electronics. Needless to say, if the users themselves rarely read the accompanying instructions for TVs, not to mention the observance of operating conditions. The Soviet past has taught many to self-repair, hitting the box in order to "improve the quality of work." But this is fundamentally wrong, because today the manufactured products are technologically advanced, quite sensitive to any mechanical influences, so even one inept intervention in the case or a blow to it can create a lot of trouble for the owner. One of the existing signs of a human factor, as a rule, or a power surge in the network, is the lack of sound for the video. The power supply of a modern TV, whether it is a plasma panel or LCD, LED TV, is a switching power supply with a given range of output supply voltages and a rated power delivered to the load for each of them. The power board can be made as a separate unit, which is typical for receivers with small diagonals, or integrated into the television chassis and located inside the device.

Typical symptoms of a malfunction of this unit are as follows:

The TV does not turn on when the power button is pressed

The standby LED is on, but there is no transition to the operating mode

Noise in the image in the form of kinks and stripes, background sound

There is sound, but no image, which may appear after a while

Requires several attempts to turn on for the appearance of a normal picture and sound

Let's analyze the circuitry of a standard power supply and its typical malfunctions using the ViewSonic N3260W TV as an example.

To fully view the diagram, you can open it in a new window and enlarge it, or download it to your computer or mobile device

The first thing to start with is a thorough visual inspection of the board on the device turned off from the network. To do this, the unit must be removed from the TV by disconnecting the connectors, and it is imperative to discharge the high-voltage capacitor in the filter - C1. In the blocks of this series of TVs, the electrolytic capacitors of the filters of the secondary power supplies often fail. They are easily diagnosed by the swollen top cover. All capacitors, the appearance of which is in doubt, must be replaced immediately.

The standby unit is made on IC2 (TEA1532A) and Q4 (04N70BF) with 5V output voltage stabilization elements on the IC7 optocoupler and the ICS3 EA1 controlled zener diode. The missing or underestimated voltage at the output of this node, measured on capacitors CS22, CS28, indicates its incorrect operation. The experience of restoring this section of the circuit indicates that the most vulnerable elements are IC2, Q7, ZD4 and Q11, R64, R65, R67, which require verification and replacement if necessary. The operability of the parts is checked by the tester directly on the unit board. At the same time, questionable components are soldered and tested separately, in order to exclude the influence of neighboring circuit elements on their performance. IC2 is simply replaceable.

If there is a 5V voltage output at the output of the standby mode circuit, a red LED lights up on the front panel of the TV. On command from the remote control or a button on the front panel of the TV, the power supply must switch to operating mode. This command - Power_ON - in the form of a high potential of about 5V comes to 1 pin of the CNS1 connector, opening the keys on QS4 and Q11. At the same time, supply voltages are applied to the IC3 and IC1 microcircuits, transferring them to the operating mode. To pin 8 of IC3 directly from the collector of Q11, to pin 12 of IC1 through the Q9 switch after starting the PFC circuit. The performance of the Power Factor Correction circuit is indirectly determined by the increase in voltage from 310 to 390 volts measured across capacitor C1. If the output supply voltages of 12V and 24V appear, then the main source on IC3, Q1, Q2 is functioning normally. Practice shows the low reliability of the UCC28051 and LD6598D in critical conditions, when the filtering of secondary sources deteriorates, and their replacement is of an ordinary nature.

Summarizing the experience of repairing television power supplies, it should be noted that the weakest link in their composition is the filter capacitors, which lose their properties and nominal parameters over time. Sometimes a faulty "capacity" is visible by a swollen lid, sometimes not. The consequences of poor filtering of the rectified voltage can be very different: from the loss of performance of the power source itself, to damage to the elements of the inverter or software failure in the memory chips on the motherboard.
Diagnostics and repair of T-con

Diagnosing a malfunction in a timing controller can sometimes be extremely difficult. The fact is that the connection of this block with the main board and the LCD matrix is ​​so great that it is sometimes not possible to visually determine what is the source of the defect. Only measurements at the T-con control points can indirectly indicate its inoperability. When repairing the matrix controller yourself, you must have a large amount of information that, with a careful and painstaking search, the Internet can provide. The controller itself is considered an integral part of the LCD panel, and manufacturers do not provide wiring diagrams for this unit. This situation makes the telemaster, when repairing this unit, be guided primarily by his professional instinct and experience in such repairs.

If your TV began to show a low-contrast, negative, whitish image with moiré patterns of various shades in the light or dark areas of the picture, it is likely that the matrix controller unit is not working correctly. To exclude the influence of the motherboard and to carry out diagnostics, many manufacturers of LCD matrices provide for the inclusion of T-con in offline mode. In this case, the cable connecting these boards is removed, only the supply voltage is supplied to the controller, and by closing the service contacts, the panel is put into test mode. When the LCD panel is in good condition and the timing of the controller, the self-diagnosis of the panel is observed on the screen in the form of alternating colored fields and stripes, as from a test television signal generator. Each name of the LCD panel has its own method of entering the test mode.

To eliminate the influence of the LCD panel on the matrix controller when measuring the supply voltage of the drivers or the reference voltages for the DAC drivers, a short-term disconnection of the loops, one or two, on the LCD panel is used. By the nature of the change in instrument readings and the visual perception of the image on the screen, certain conclusions can be drawn about the causes of the malfunction. For reliable control of the unit's performance during measurements, it is necessary to control the presence, shape, amplitude, frequency and duty cycle of pulses, which can be carried out using an oscilloscope. The presence of an oscilloscope facilitates the search for a defect and is always used for diagnostics in a stationary service center.

In some cases, it is necessary to doubt the health of the matrix controller in the absence of an image with a dark or very light (white) monitor screen. It is necessary to control the passage of the supply voltage from the main board and the formation of secondary voltages by DC / DC converters in the block itself. Sometimes problems with the timing controller, and even with the matrix itself, can arise due to the fault of the owner who is too careful, wiping the TV screen with a too damp cloth, or, conversely, careless, spilling liquid on the LCD panel or inside the device. If moisture gets on the matrix, irreparable consequences can occur in the form of destruction of conductive loops, their corrosion, shorting of drivers and failure of the matrix controller due to a critical violation of its operation mode.

Repair of the timing controller is not provided by the manufacturer of LCD matrices, only its replacement. Therefore, technical information on the restoration of the block is not provided and there are no diagrams for it. However, in our workshop, every opportunity is used to repair the TV at the component level without replacing blocks and boards. When restoring, technical information is used in the form of "datasheets" - descriptions, characteristics, connection diagrams of the components that make up the controller, which allows the telemaster to successfully carry out repair work on such a complex unit of a modern TV as T-con.

As in the investigation of crimes, in our case it is important to establish everything to the smallest detail: how did the malfunction occur, what preceded it, what is the nature of its manifestation? This information will be needed by a specialist to accurately localize the source of all troubles in TV. Also, this is important when carrying out self-repair of the TV. First, you should accurately determine the "broken" part. As practice shows, in 80% of cases the sound on the TV disappeared due to three types of malfunctions. Let's look at each of them in detail. The first is caused by failures in the operation of the radio channel, damage to the effects processor, the entire mechanism of the central processor is possible, and occasionally there are failures in memory processing. The second is a malfunction of the speaker, which is caused by wear, contact separation, burnout. The third is the breakdown of microcircuits, and there are quite a few factors preceding this, starting with network outages, power surges, and ending with a short circuit, failure of capacitors or, again, contacts.

But back to the topic of the article and begin to act. Our first priority is to restore the sound on the TV, the source is approximately installed, which means it's time to repair. We unscrew the case with tools and carefully remove it without touching the rest of the blocks. We look at the details and visually look for potential breakdowns. If they are not there, we proceed to check the operability of the circuits and blocks, in the absence of responses, we pay attention to the contacts, even if they are connected, they can be “cold”, which means the circuit itself is not working. When such situations are detected, we change the scheme or try to debug it

No picture on the TV screen - one of the most frequent breakdowns of this type of equipment, regardless of models and brands.

There are many possible reasons for the disappearance of the image on the screen. Very often causes a malfunction lack of screen backlight.

Repair of the backlight of the TV belongs to the category of particularly complex. Trusting him to a non-professional is extremely dangerous. On your own, without having the appropriate knowledge, experience and tools, it is impossible to perform it.

Therefore, if your TV turns on, responds to the remote control, there is sound, but there is no video, the best solution is to contact the VseRemont24 service center!

Two causes of TV backlight failure

With high-quality TVs, the image disappears after many years of flawless operation. Unfortunately, cases when a new technique ceases to show happen at least (if not more often).

It may not even take a year (!) How your TV will break if you are not lucky enough to buy low-quality equipment.

Most modern LCD TVs have a backlight. LED (light emitting diode). It is these models that dominate the Russian market of household appliances.

The LCD TV screen is a liquid crystal matrix, which is illuminated from the inside by rows of soldered LED strips.

Simply put, LED backlight- this is a lot of small diode bulbs located on the TV behind the liquid crystal matrix.

Total TV backlight failure options two:

1. Some of the LEDs burned out. The LEDs are connected in series, so the breakage of any of them entails the failure of the entire LED backlight. At the same time, a voltage of about 200 volts continues to flow to the light bulbs.
2. Problems with the backlight control driver (LED driver). In this case, no voltage is supplied to the LEDs, so they do not light up.

It is not difficult to make sure that the lack of an image is due to a backlight malfunction. Point the flashlight at the screen of a working TV. Having carried out forced illumination, you will make out the image.

This completes the self-diagnosis. Next, you need to invite a master who will diagnose the TV by disassembling it.

Professional TV backlight repair

The specialist will remove the stand and the back cover of the TV, disconnecting the cable from the joystick from it. Will become available three TV boards:

• power supply, on the board of which the backlight driver is assembled,
• main board,
• t-con matrix control board.

Board dismantling- a very painstaking task that requires maximum concentration of attention. Any inaccurate movement can lead to the final breakdown of the TV (for example, a cable break). Even a simple touch to the matrix with dirty hands will subsequently result in poor image quality.

An experienced specialist will carefully remove:

1. T-con. Disconnect the cables, unscrew the bolts.
2. Metal protection with decoders. Loosen the screws on the sides.
3. TV front frame. Unscrew the fastening bolts around the contour.
4. Decoders with rubber mounts. To do this, the master carefully turns the screen over, holding the matrix.
5. Scattering film. First you need to snap off the latches and remove the plastic frame.
6. Reflector. Remove retaining clips.

After these steps, nothing will stop you from starting checking the backlight of the TV.

Sometimes the problem of LED burnout is visible to the naked eye - one or more bulbs burn at the point of attachment, the color of their lenses changes, they melt.

If there are no visible traces of individual diodes, you will have to check all LED bulbs.

First, the power supply is connected to each line of LEDs. What line not caught fire, in that open and / or short circuit.

After that, power is supplied in turn to each LED from the faulty line. Which LED does not burn, that one is wrong.

The lens is removed, and the faulty diode itself is soldered (a soldering dryer is used for this). Then a new one is soldered in place of the faulty LED. The lens is glued to its original place.

TV backlight repair completed!

After the master checks the operability of the backlight (voltage is applied) and assembles the TV in the reverse order.

If the TV is displayed and there are no light or dark spots anywhere on the screen, the repair was successful!

If, according to the results of the diagnostics, it turns out that everything is in order with the line of LEDs, the problem is hidden in driver in the power supply.

Each LED driver is unique. After checking with a multimeter, a preliminary analysis of the circuitry is necessary. Next, changes in the current in the LED lines are carried out, based on the data obtained, and all necessary repairs or replacement of parts.

Did you know that some TV dealers specifically set the screen backlight level to maximum position in all modes to speed up the failure of the LEDs and bring the hour of repair closer?

Maximum brightness contributes to premature failure of the LED backlight. Therefore, in a repaired TV set, not too large (optimally 75% ) brightness.