CRT TV image disappears. What to do if the image on your LG TV disappears, but there is sound?

Why there is no picture on the TV, but there is sound: 8 reasons

A breakdown often occurs when the TV has sound but no picture. Despite the fact that a variety of TV models are constantly going on sale, which are literally considered to be improvements over older designs for watching TV, quite often one has to deal with many problems. For example, there is no image on the TV, but there is sound, a horizontal bar appears on the screen, or the plasma has failed due to high voltage. What to do in such a situation? It is worth familiarizing yourself with what malfunctions can occur, why they occur and how to fix them.

TV malfunctions

The reason for a broken TV can sometimes be very different.

You can get acquainted with the main malfunctions in the operation of the TV yourself using the Internet.

And most often it doesn't work because:

• Malfunctions in the functioning of the control unit;
• Power supply burnout;
• Problems in such a part as a video amplifier;
• Broken radio channel selector;
• Malfunctions in the module responsible for the color in the pictures or in the sync pulse selector;
• Failure of the color module;
• Malfunctions in the frame and line scanning unit;
• TV matrix failures.

If you do not have independent skills in diagnosing a TV, then defects and malfunctions should be examined by a specialist with experience, appropriate education and the necessary equipment. If the breakdown does not have characteristic features, then repairs will not require major investments. However, if a malfunction requires replacement of a part, and it is far from cheap, then in some cases the technicians even recommend leaving the equipment for write-off and purchasing new equipment, since the likelihood that the problem will not arise again is very high.

There is sound on the LCD TV, but no picture: reason

It is not difficult for an experienced specialist to find typical breakdowns, however, what to do if the screen of plasma TVs does not show, but there is sound? It is not always possible to determine on your own why the picture is missing, since LCD devices have a complex structure and many microcircuits, the diagnosis of which requires special equipment and operational experience. The optimal solution is to contact a specialist.

Failure may be of another type. For example, the TV turns on, and then starts blinking or goes out completely. Regardless of the type and model of the device, diagnostics are needed, as this may indicate a serious malfunction.

The problem of lack of image can appear even on well-known and popular brands of TVs

Owners of products even from such well-known brands as:

• Samsung;
• Phillips;
• Erickson;
• Thomson;
• Onyx;
• Supra;
• Lji Flatron and others.

There are a number of reasons why the screen has gone dark, but the TV has not stopped working and there is sound. The cord was disconnected from the socket, damage appeared on the wire, the inverter, which is responsible for supplying voltage to the lamp, failed and, accordingly, it does not light up. There may be a malfunction in the matrix, system board or backlight unit.

There may also be the following reasons: there are defects in the convector, the cable and decoder are damaged, the electrolyte in the power supply is broken, the electrolytic capacitor has become unusable. In CRT TVs, the vertical and horizontal scanning may be damaged, or the cable and matrix may be disconnected.

Why the TV doesn't work: diagnostics

If there is sound when you turn on the LCD TV, but there is distortion on the screen or it does not light up at all, then you can take a number of actions that can fix the problem. They must be done carefully and only in accordance with the recommendations of specialists.

To find out the cause of the TV failure, you need to diagnose it

Diagnostics:

1. The quality of the connecting cable is checked. If it is damaged, replacement is required.
2. On the panel located at the back, you need to inspect the junction of the cord with the socket.
3. Next, the volume is increased to maximum, after which the device should return to normal operation.
4. All mechanical impacts on the TV, even if they are minor, are strictly prohibited.
5. You need to check the device settings for turning on and off the output and input channels.

If there are frequent power outages, you need to install a fuse.

Horizontal stripe on TV screen

If horizontal stripes begin to appear on the screen, cutting off half of the image, then you need to immediately search for this malfunction.

The color of the dash can be:

• Red;
• Pink;
• White.

If you notice a horizontal stripe on the TV screen, you need to contact a technician for help.

Depending on the type of TV, the cause of this breakdown may be different. For picture tubes, a horizontal strip indicates that there is a defect in the frame scanning, which can occur due to obsolescence of parts or due to strong and frequent surges in voltage. The breakdown is not difficult to fix and can be done at minimal cost.

If it is an LCD, plasma orLED/ LCD and horizontal stripes have formed, this indicates a malfunction:

• Matrices;
• TDKS;
• Boards called T-KON.

In the first case, a complete replacement of the screen is required, but if it is possible to restore the operation of the device, then a lot of money is needed. In this case, you need to decide whether to repair the device or purchase new equipment in order to save money.

• Samsung;
• West;
• Philips.

It is strictly unacceptable for the TV to fall on the floor, as this will cause the device to turn off, and will also cause major damage, which is not so easy to fix. It is very important to keep the equipment clean, since dust penetrating inside the device can cause clogged contacts, short circuits and overheating of the cable.

It is advisable that the TV be installed in a place where there will not be even minimal mechanical impact. It is best to install it on the wall using special brackets. It is not advisable to wet clean the TV, regardless of its type. Dust is removed with a vacuum cleaner.

Common malfunctions of LCD TVs and their elimination

As already mentioned, all TV models can break down, be it: CW71A, EBR73575201, CW62C, MAX9590, TA8750AN.

It is worth noting that there are an incredible number of faults that exist and may arise and these include:

• Ripple;
• The process when the screen snows;
• Lines that are located vertically;
• The TV beeps;
• The screen narrowed;
• For color screens, the tuner frame does not open;
• The screen either goes dark or lights up too brightly and others.

Using the Internet, you can independently familiarize yourself with common malfunctions of LCD TVs

There are also malfunctions that can occur exclusively in LCD TVs. Failure of the matrix backlight circuit or, in other words, the TV inverter. The inverter is used to convert the low voltage that comes from the power supply to a higher one in order to ignite and maintain the glow of the lamp that illuminates the screen. Failure can be of various types.

For example, after turning on the device, the screen becomes dark or immediately black, and partially, not completely. This indicates that it is not the picture that disappears, but the backlight that does not work.

It is possible that the power supply, which supplies voltage to each node in the LCD TV, may fail. The power supply has several degrees of protection, which may not always work properly. If we consider malfunctions caused specifically by a defect in the functioning of the power supply, then such problems are possible as: the inability to turn on the TV, the screen not turning on or blinking, turning on after a long delay, turning off on its own, the device does not respond to the buttons pressed on it or simply does not perform task, the image disappears.

The main module, which is responsible for controlling the entire TV as a whole, may break down. It says a lot that it is faulty. For example, the lack of functioning of components such as an inverter, timing controller and power supply. The main module board contains a central processor, converters, a tuner device, temporary and permanent memory, and software. A malfunction in the main unit can manifest itself in the form of noise in the picture and difficulties in controlling the TV.

A breakdown of the matrix or, in other words, the timing controller is considered a serious problem that requires immediate contact with a technician. Due to the timing controller, the signal is converted and sent to the main board, which affects the quality of the reproduced image. Therefore, if the screen is covered with goosebumps, ripples and other defects, then you first need to start diagnostics with the matrix.

Why is there no picture on the TV, but there is sound (video)

So, diagnostic methods, depending on the breakdown, can be different, for example, to detect the reverse path of the beam, you need a special device, and to eliminate a crack on the screen, only a visual inspection and nothing more. The most important thing is that a non-working TV has an excellent technician who can get the product working again quickly and without mistakes.

Similar materials

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

TVs often have this problem - there is sound, but no picture. As a rule, with such a malfunction, the screen does not light up, but everything else works - there is sound, channels are switched, DVD works, etc.

Types of breakdowns

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

· the screen may become one color;

· the image is compressed into a narrow strip;

· the picture suddenly starts blinking;

· the picture is there, but it’s almost invisible;

· There are 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 backlight lamps themselves. The screen may go dark due to a malfunction of other components.

When an LCD TV has sound but no picture, in 90% of cases repairing 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 you need to tell him is the address, time of desired arrival and information about the breakdown. It is also necessary to inform him that there is sound, but no image. Don’t worry, because you have witnessed a very common type of malfunction in many LCD TVs and monitors. Although the very statement about the complete absence of an image is not entirely true. There are types 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 colors, blurring of brightness and contrast.

The main reason is the lack of backlighting and the malfunction of its parts. There are many mechanisms in this part of the TV, including backlight lamps, inverters that supply voltage to the lamps, and, of course, contacts. But there are also special cases in which failures are caused by other broken blocks or TV circuits.

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

Definitely - repair of the power supply, inverter, backlight lamps, updating of contacts. If this does not help, or these parts are intact and in good working order, it is necessary to repair the vertical or horizontal scanning unit. This 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 the right conclusion about the breakdown. And if the monochromaticity described above occurs (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, problems often arise in the matrix, which is often due to exhaustion of resources or the human factor. Impacts on a faulty box only aggravate the breakdown, which is confirmed by the identification of faults where, in fact, they should not exist. High-tech plasmas (LCDs) are not designed to withstand physical deformation, be careful when handling such equipment. In case of incompetence, we advise you to refrain from interfering with the holy of holies of technology - the internal component. Call a specialist to your home, each of them is a specialist in urgent repairs. The advantages of this method of TV repair are not at all in the guarantee, not even in the speed and quality of the work performed, but, first of all, in accessibility. The services of professionals are aimed at helping people at a reasonable, affordable price. They are a relief from unnecessary work and headaches for owners of broken models.

The inverter in a TV is a device for starting and stable operation of fluorescent lamps for the backlight of an LCD panel. Ensures the 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 repairing a television receiver inverter yourself, you need to know the functions it performs.

Tasks of the television inverter:

O conversion of DC voltage 12 - 24 volts into high voltage AC

O stabilization and adjustment of lamp current

O Backlight brightness adjustment

O Provides overload and short circuit protection

Electrical circuit 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. Through connector CN1, 12 volt power (F1), a power command (ON/OFF), and constant voltage (Dimm) are supplied to adjust the brightness. The protection unit (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 at U1 is blocked, and the inverter will be in a protection state. The node is blocked when the supply voltage is low, when the supply voltage drops when the load is turned on, when the converter is overloaded or there is a short circuit.

Characteristic signs of inverter malfunction

· Backlights do not turn on

Backlights turn on and off briefly

· Unstable brightness and screen flickering

· The inverter periodically does not turn on after a long period of inactivity

· Uneven screen illumination with 2-inverter circuit

Features of inverter unit repair

When diagnosing faults related to the correct operation of the inverter, you should first of all make sure that there is no ripple in the supply voltage and that it is stable. Pay attention to the passage of startup commands and backlight brightness control from the motherboard. Eliminate the influence of backlight lamps by using their equivalent in cases where the problem is not clear. Take advantage of the opportunity to remove protection from the inverter during repairs to determine the defective part. Don’t 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 careful inspection of the board, you can see “burnt out” parts that need to be replaced. Very often field-effect transistor switches fail, but sometimes replacing them does not always lead to a positive result. The functionality of the unit may be restored for an indefinite period of 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 you have doubts about the success of the matter, call a technician who has already repaired similar devices many times and knows all the “pitfalls and shoals” thanks to his accumulated experience and professional knowledge.

High-voltage transformers are considered the weak link in the inverter units. Operation under high voltage conditions requires special assembly quality of these components and places high demands on the insulation properties. In addition, it should be said that transformers can become noticeably heated during operation of the backlight. Defects such as a break or inter-turn short circuit of the windings of these parts are commonplace. Diagnostics of these elements can be complicated by the fact that a short circuit or break can only be observed in operating mode, and “diagnosis” of them in a de-energized state will not reveal problems with them. Here, swapping the dubious and serviceable transformer and further analyzing the situation can come to the rescue.

Different TVs use inverters with different numbers of transformers. In small-sized devices, the inverter can contain 2 - 4 transformers; in large-diagonal TVs, especially of previous years of production, there were up to 20 similar products. Naturally, a large number of them reduces the reliability of the circuit as a whole, so in modern models their use is reduced to a minimum through innovative technical solutions.

A sign 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 in this case no sound appears. The nature of the defect is different, and the source may still be the same inverter unit. Some TV models contain a feedback signal from the inverter to the motherboard processor, indicating malfunctions in its operation. Without receiving confirmation from the inverter that everything is fine with it, the processor changes the TV’s operating mode to standby or displays error messages through LED indicators. For some manufacturers, after a certain number of unsuccessful starts, the system may stop sending a command to turn on the backlight until errors are reset or the memory is cleared.

TYPICAL PROBLEMS RELATED TO THE BACKLIGHT.
The matrix is ​​the most expensive part, and before opening the matrix and looking at the lamp, you need to determine whether the backlight lamp is faulty, and to do this you need to make sure of this by connecting the matrix to a previously working backlight module, or connecting a previously working backlight lamp instead of your matrix . Malfunctions of backlight modules and so on will be discussed later.
The malfunction of the backlight is often easy to determine visually; a pink or closer to red background of the matrix or darkening at the edges of the matrix is ​​a prerequisite for the fact that the backlight or high-voltage converter (matrix backlight module) in your matrix will soon die 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 (bending, impact, fall) and, as a result, a broken backlight lamp. In this case, when disassembling the matrix, you need to 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 LIGHT LAMP.

Replacing a backlight lamp is not a complicated or time-consuming procedure at first glance, but let’s look at all this in more detail.
To replace the lamp you need: Experience in carrying out this work, knowledge of the matrix structure, a clean and dust-free workplace, or a special mechanical device. I was repeatedly brought matrixes after an unqualified lamp replacement, and in 60% of cases the matrix only had to be replaced; in other cases, repairing the damage was more expensive than a regular lamp replacement.

According to the manufacturers, the matrix backlight lamp is an element of the matrix design and must be replaced along with the matrix, i.e. The matrix manufacturer does not provide for lamp replacement under non-production conditions. The backlight lamp is installed inside the reflective container and glued to the light-refracting and other filters and reflectors of the screen. An attempt to remove the lamp may result in damage to the filter arrangement, or to the filters themselves, and the image quality of the matrix will greatly deteriorate. When replacing a backlight lamp, people with no experience often damage the cables connecting the glass to the decoder, which will result in damage to the matrix

The inverter is a complex electronic device, which can cause some difficulties when repairing it yourself. 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 recall the experience of repairing similar devices, be guided by the general principles of their circuit design solutions and use the database of datasheets for backlight driver microcircuits and key transistors.

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

The high quality standard in the production of televisions, which has recently become the norm, is not a panacea for failures, problems and defects that sometimes arise in any electronics. What can we say if the users themselves rarely read the accompanying instructions for televisions, not to mention compliance with the operating conditions. The Soviet past taught many to do their own repairs, hitting the box in order to “improve the quality of work.” But this is fundamentally wrong, because today the products produced are technologically advanced, quite sensitive to any mechanical influences, so even one inept intervention in the body or a blow to it can create a lot of trouble for the owner. One of the existing signs of the human factor, as a rule, or a power surge in the network, is the absence of audio accompaniment to the video. The power supply of a modern TV, be it a plasma panel or LCD, LED TV, is a switching power supply with a given range of output supply voltages and the rated power supplied to the load for each of them. The power board can be made in the form of a separate block, this is typical for small diagonal receivers, or integrated into the television chassis and located inside the device.

Typical symptoms of a malfunction of this unit are the following:

· The TV does not turn on when you press the power switch

· The standby LED is on, but there is no transition to 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

· It takes several attempts to turn on for normal picture and sound to appear.

Let's look at the circuitry of a standard power supply and its typical faults 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 you should start with is a thorough visual inspection of the board with the device disconnected from the network. To do this, the unit must be removed from the TV by disconnecting the connectors, and be sure to discharge the high-voltage capacitor in the filter - C1. In units of this series of TVs, the electrolytic capacitors of the secondary power supply filters quite often fail. They are easily diagnosed by a swollen top cover. All capacitors whose appearance is questionable must be replaced immediately.

The standby mode unit is made on IC2 (TEA1532A) and Q4 (04N70BF) with elements for stabilizing the 5V output voltage on the optocoupler IC7 and the controlled zener diode ICS3 EA1. Missing or low voltage at the output of this unit, measured on capacitors CS22, CS28, indicates its malfunction. The experience of restoring this section of the circuit shows that the most vulnerable elements are IC2, Q7, ZD4 and Q11, R64, R65, R67, which require checking and replacement if necessary. The performance of the parts is checked by a tester directly on the unit board. In this case, questionable components are soldered off and tested separately to eliminate the influence of neighboring circuit elements on their performance. IC2 chip simply needs to be replaced.

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

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 the faulty “container” is visible from the swollen lid, sometimes not. The consequences of poor filtering of the rectified voltage can be very different: from loss of functionality of the power supply itself, to damage to the inverter elements or software failure of memory chips on the motherboard.
T-con diagnostics and repair

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 T-con control points can indirectly indicate its inoperability. When repairing a matrix controller yourself, you need to have a large amount of information, which the Internet can provide with a careful and painstaking search. The controller itself is considered an integral part of the LCD panel, and manufacturers do not provide electrical diagrams for this unit. This situation forces the teleworker, when repairing this unit, to be guided primarily by his professional instincts and experience in similar repairs.

If your TV begins to show a low-contrast, negative, whitish image with moire of various shades in light or dark areas of the picture, there is a high probability that the matrix controller unit is not working correctly. To exclude the influence of the motherboard and carry out diagnostics, many manufacturers of LCD matrices provide for turning on the 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 the panel is entered into test mode by closing the service contacts. If the LCD panel and timing controller are working properly, the panel’s self-diagnosis is observed on the screen in the form of alternating colored fields and stripes, as from a television test signal generator. Each type of LCD panel has its own method of entering test mode.

To eliminate the influence of the LCD panel on the matrix controller when measuring the driver supply voltage or reference voltages for the DAC drivers, use a short-term disconnection of the cables, one or two, on the LCD panel. Based on the nature of changes in instrument readings and the visual perception of the image on the screen, one can draw certain conclusions about the causes of the malfunction. To reliably monitor the performance of a unit when taking measurements, it is necessary to control the presence, shape, amplitude, frequency and duty cycle of pulses, which can be done using an oscilloscope. The presence of an oscilloscope makes it easier to find a defect and is always used for diagnostics in a stationary service center.

In some cases, doubt about the serviceability of the matrix controller occurs due to the absence of an image when the monitor screen is dark or very light (white). 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 unit itself. Sometimes problems with the timing controller, and even with the matrix itself, can arise due to the owner being too careful, wiping the TV screen with a too damp cloth, or, conversely, being 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 current-carrying cables, their corrosion, short-circuiting of drivers and failure of the matrix controller due to a critical violation of its operating mode.

Repair of the timing controller is not provided by the manufacturer of the LCD matrices, only its replacement. Therefore, technical information on restoring the block is not provided and there are no diagrams for it. However, in our workshop we use every opportunity to repair a TV at the component level without replacing blocks and boards. During restoration, technical information is used in the form of “datasheets” - descriptions, characteristics, connection diagrams of components included in the controller, which allows the TV technician 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 down to the smallest detail: how did the malfunction arise, what preceded it, what was the nature of its manifestation? A specialist will need this information to accurately localize the source of all troubles on TV. This is also important when carrying out independent TV repairs. First, you should accurately determine the “broken” part. As practice shows, in 80% of cases the sound on the TV disappears due to three types of malfunctions. Let's take a closer look at each of them. The first is caused by malfunctions in the radio channel, damage to the effects processor, the entire central processing unit mechanism is possible, and occasionally failures occur during memory processing. The second is a malfunction of the speaker, which is caused by wear, contacts coming off, or 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 short circuits, failure of capacitors or, again, contacts.

But let’s return to the topic of the article and start taking action. Our first priority is to restore the sound supply on the TV; the source has been approximately identified, which means it’s time to repair. Using tools, unscrew the housing and carefully remove it without touching the remaining blocks. We look at the details and visually look for potential breakdowns. If they are not there, we proceed to check the functionality of the circuits and blocks; if there are no responses, we pay attention to the contacts; even if they are connected, they may be “cold”, which means the circuit itself is not working. If such situations are detected, we change the circuit or try to debug it

Despite the fact that a variety of TV models are constantly going on sale, which are literally considered to be improvements over older designs for watching TV, quite often one has to deal with many problems. For example, there is no image on the TV, but there is sound, a horizontal bar appears on the screen, or the plasma has failed due to high voltage. What to do in such a situation? It is worth familiarizing yourself with what malfunctions can occur, why they occur and how to fix them.

The reason for a broken TV can sometimes be very different.

And most often it doesn't work because:

• Malfunctions in the functioning of the control unit;
• Power supply burnout;
• Problems in such a part as a video amplifier;
• Broken radio channel selector;
• Malfunctions in the module responsible for the color in the pictures or in the sync pulse selector;
• Failure of the color module;
• Malfunctions in the frame and line scanning unit;
• TV matrix failures.

If you do not have independent skills in diagnosing a TV, then defects and malfunctions should be examined by a specialist with experience, appropriate education and the necessary equipment. If the breakdown does not have characteristic features, then repairs will not require major investments. However, if a malfunction requires replacement of a part, and it is far from cheap, then in some cases the technicians even recommend leaving the equipment for write-off and purchasing new equipment, since the likelihood that the problem will not arise again is very high.

There is sound on the LCD TV, but no picture: reason

It is not difficult for an experienced specialist to find typical breakdowns, however, what to do if the screen of plasma TVs does not show, but there is sound? It is not always possible to determine on your own why the picture is missing, since LCD devices have a complex structure and many microcircuits, the diagnosis of which requires special equipment and operational experience. The optimal solution is to contact a specialist.

Failure may be of another type. For example, the TV turns on, and then starts blinking or goes out completely. Regardless of the type and model of the device, diagnostics are needed, as this may indicate a serious malfunction.

Owners of products even from such well-known brands as:

• Samsung;
• Phillips;
• Erickson;
• Thomson;
• Onyx;
• Supra;
• Lji Flatron and others.

There are a number of reasons why the screen has gone dark, but the TV has not stopped working and there is sound. The cord was disconnected from the socket, damage appeared on the wire, the inverter, which is responsible for supplying voltage to the lamp, failed and, accordingly, it does not light up. There may be a malfunction in the matrix, system board or backlight unit.

There may also be the following reasons: there are defects in the convector, the cable and decoder are damaged, the electrolyte in the power supply is broken, the electrolytic capacitor has become unusable. In CRT TVs, the vertical and horizontal scanning may be damaged, or the cable and matrix may be disconnected.

Why the TV doesn't work: diagnostics

If there is sound when you turn on the LCD TV, but there is distortion on the screen or it does not light up at all, then you can take a number of actions that can fix the problem. They must be done carefully and only in accordance with the recommendations of specialists.

Diagnostics:

1. The quality of the connecting cable is checked. If it is damaged, replacement is required.
2. On the panel located at the back, you need to inspect the junction of the cord with the socket.
3. Next, the volume is increased to maximum, after which the device should return to normal operation.
4. All mechanical impacts on the TV, even if they are minor, are strictly prohibited.
5. You need to check the device settings for turning on and off the output and input channels.

If there are frequent power outages, you need to install a fuse.

Horizontal stripe on TV screen

If horizontal stripes begin to appear on the screen, cutting off half of the image, then you need to immediately search for this malfunction.

The color of the dash can be:

• Red;
• Pink;
• White.

Depending on the type of TV, the cause of this breakdown may be different. For picture tubes, a horizontal strip indicates that there is a defect in the frame scanning, which can occur due to obsolescence of parts or due to strong and frequent surges in voltage. The breakdown is not difficult to fix and can be done at minimal cost.

If it is an LCD, plasma orLED/ LCD and horizontal stripes have formed, this indicates a malfunction:

• Matrices;
• TDKS;
• Boards called T-KON.

In the first case, a complete replacement of the screen is required, but if it is possible to restore the operation of the device, then a lot of money is needed. In this case, you need to decide whether to repair the device or purchase new equipment in order to save money.

• Samsung;
• West;
• Philips.

It is strictly unacceptable for the TV to fall on the floor, as this will cause the device to turn off, and will also cause major damage, which is not so easy to fix. It is very important to keep the equipment clean, since dust penetrating inside the device can cause clogged contacts, short circuits and overheating of the cable.

It is advisable that the TV be installed in a place where there will not be even minimal mechanical impact. It is best to install it on the wall using special brackets. It is not advisable to wet clean the TV, regardless of its type. Dust is removed with a vacuum cleaner.

Common malfunctions of LCD TVs and their elimination

As already mentioned, all TV models can break down, be it: CW71A, EBR73575201, CW62C, MAX9590, TA8750AN.

It is worth noting that there are an incredible number of faults that exist and may arise and these include:

• Ripple;
• The process when the screen snows;
• Lines that are located vertically;
• The TV beeps;
• The screen narrowed;
• For color screens, the tuner frame does not open;
• The screen either goes dark or lights up too brightly and others.

There are also malfunctions that can occur exclusively in LCD TVs. Failure of the matrix backlight circuit or, in other words, the TV inverter. The inverter is used to convert the low voltage that comes from the power supply to a higher one in order to ignite and maintain the glow of the lamp that illuminates the screen. Failure can be of various types.

For example, after turning on the device, the screen becomes dark or immediately black, and partially, not completely. This indicates that it is not the picture that disappears, but the backlight that does not work.

It is possible that the power supply, which supplies voltage to each node in the LCD TV, may fail. The power supply has several degrees of protection, which may not always work properly. If we consider malfunctions caused specifically by a defect in the functioning of the power supply, then such problems are possible as: the inability to turn on the TV, the screen not turning on or blinking, turning on after a long delay, turning off on its own, the device does not respond to the buttons pressed on it or simply does not perform task, the image disappears.

The main module, which is responsible for controlling the entire TV as a whole, may break down. It says a lot that it is faulty. For example, the lack of functioning of components such as an inverter, timing controller and power supply. The main module board contains a central processor, converters, a tuner device, temporary and permanent memory, and software. A malfunction in the main unit can manifest itself in the form of noise in the picture and difficulties in controlling the TV.

A breakdown of the matrix or, in other words, the timing controller is considered a serious problem that requires immediate contact with a technician. Due to the timing controller, the signal is converted and sent to the main board, which affects the quality of the reproduced image. Therefore, if the screen is covered with goosebumps, ripples and other defects, then you first need to start diagnostics with the matrix.

Why is there no picture on the TV, but there is sound (video)

So, diagnostic methods, depending on the breakdown, can be different, for example, to detect the reverse path of the beam, you need a special device, and to eliminate a crack on the screen, only a visual inspection and nothing more. The most important thing is that a non-working TV has an excellent technician who can get the product working again quickly and without mistakes.

Professional TV master In his work, he always uses a creative, comprehensive approach to diagnosing various types of faults, including defects associated with the absence of an image in the presence of sound and vice versa. To determine the source of the breakdown, it is necessary to assess the general state of affairs, without losing sight of a single detail. Almost always, when a well-functioning mechanism, such as a modern TV, malfunctions, in addition to the main problem visible to the naked eye, there are also small nuances, the knowledge and identification of which contribute to the success of the case, helping to localize the weak link and calculate the affected area of ​​​​the electrical circuit.

Invaluable assistance in analyzing the situation is provided by a specialist’s knowledge of typical faults of a given model and the chassis of the device. It is no secret that certain series and brands of televisions have “diseases” that are unique to them. Possession of this knowledge helps to carry out diagnostics at lightning speed, find the “burnt out” part and replace it, “transferring the patient from the intensive care unit to the convalescent ward.” However, the range of possible conflicts that arise in the device is so wide that only a small part of them can be subject to such “treatment”. For the rest, the only solution remains painstaking work to assess the functionality of individual components and sections of the circuit, analyzing their condition, electrical measurements, taking into account minor factors that help to get the overall picture and guide the technician in the right direction.

No picture, there is sound

If there is no image and there is sound on a TV with LCD or LED backlighting, you need to pay attention to the fact that the product is almost completely functional: it is controlled from the remote control and from the front panel, there is sound adjustment, but the screen is dark. In most cases, the “culprit” turns out to be the power supply unit for the LED backlight or the inverter of the LCD panel, as well as their operation in protection mode when the LEDs or lamps fail. Less common are problems with the power supply or lack of a power-on command from the motherboard.

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

No image can be caused by more than just a faulty backlight. Sometimes the cause of a dark screen may be other parts of the TV: the main board, matrix controller or LCD panel. In this situation, the backlight works, but the image is not displayed, which can be a consequence of a variety of reasons. From a malfunction in the software of the memory chips on the motherboard to a malfunction of the reference voltage generator for the DAC drivers, defects in the voltage generation unit for powering the drivers in the T-con, or failure of LCD matrix elements. There are no ready-made recipes in this case. Only an analysis of the functionality of individual components and sections of the circuit, diagnostics of their condition, and electrical measurements will help to find the right solution for restoring the device.

No sound, there is a picture

Examining the problem of the lack of sound with a normal image, we can say that there is no wide range of typical faults here. Exceptions include breakdown of electrolytic capacitors and SMD components in power supply circuits and wiring of audio circuit microcircuits and frequent breakage of dynamic heads. Sometimes this defect is observed due to a software failure in memory chips (EEPROM, SpiFlash) and to restore their original properties requires flashing them on a programmer or replacing chips with installed software. Otherwise, the absence of a sound signal is purely individual in each case. Electrical measurements of the operating modes of ULF microcircuits, a sound processor and other elements involved in the procedure of demodulation, conversion and amplification of the audio component of a television signal will help localize the problem.

In search of solutions of this kind, a telemaster is helped by an understanding of the essence of what is happening, knowledge of circuitry, the ability to analyze and an extensive knowledge base of similar faults and methods for restoring equipment. Most of us in practical activities are guided by the principle - “Do no harm!” Extreme accuracy and caution when taking measurements, anticipating the consequences of your intervention has become the norm. We strongly recommend that people who are far from this profession do not put their TV under stress by trying to fix it themselves. Believe me, this is not so easy in modern high-tech models. We often hear the phrase: “I just don’t have a soldering iron (circuit, tester), otherwise I would fix it myself” - and we silently hide our smile. Self-repair is, of course, possible, but it mainly comes down to replacing “swollen” electrolytic capacitors, which are easily diagnosed with a quick visual inspection, or following advice gleaned from TV repair forums and electronic equipment repair resources. Our pages reveal some of the secrets of TV repair, and it’s up to you to follow them or not.

One of the most popular problems faced by owners of smart TVs from the Korean company LG is when the TV completely loses the image, but there is sound. Symptoms associated with content transfer may vary:

• The device speaks but does not show.
• Unable to change channels due to black screen.
• The backlight does not work.
• The technique distorts the picture, turns it upside down, and it becomes necessary to change the display format.
• The TV is dim and dim.
• The broadcast on the display periodically disappears and the screen does not light up.

In this article we will look at what the causes of malfunctions may be, their elimination, and also what to do in each specific situation.

The most popular reasons why an ice TV does not show digital and analog channels are considered to be faults in hardware components. Problems with the power supply or color unit, a burnt-out inverter, breakdown of matrices and capacitors - all this can lead to the following:

• Doesn't show transmissions.
• Shows them in green or black and white.
• Broadcasts an inverted image.
• Other variations, when there is no video, but the sound works (more on them later).

To solve problems when the screen does not show, the logo and subsequent broadcasts do not appear, a visit to a private technician at a repair center or self-diagnosis and repair of the breakdown on your own will help.

Testing the cable

If the sound comes out at a normal volume of audio noise, but the screen remains dark, one of the diagnostic measures will be to test the cables transmitting the picture:

1. Antenna.
2. HDMI.
3. From your cable provider.
4. We check the availability of the Internet (in the case of digital set-top boxes from providers).

To do this, you will need a special Moninfo utility. It is designed to find some problems in the transmission of audio and video signals. If the application detects failures, you should carefully examine the cable pins for damage.

Matrix failure

Perhaps the most common reason why the image disappears on an LG TV is a matrix failure. Because of this it starts:

• jump video,
• an afterimage appears on half the monitor,
• There are stripes (white, yellow, pink or multi-colored) all over the display.

As a rule, this TV part breaks under the influence of external signs: moisture, strong impacts or falls. In such cases, it will not be possible to repair the display, and you will have to replace the matrix (or, alternatively, buy new equipment). But if problems arose without any visible prerequisites, for example, the picture suddenly began to bifurcate or “go cloudy,” then they can be corrected by technical service, without replacing the module with a new one.

It is also possible to replace the matrix yourself at home, however, it will be very difficult for a non-professional to do this. The first difficulties will begin already during preparation for repair: it is quite difficult to get a suitable matrix, and it must be ordered from certified service centers. Otherwise, there is a risk of running into a fake and the work will be down the drain.

Burnt out capacitors

Problems with capacitors in LCD TVs occur due to strong power surges in the network. External signs of a malfunction appear in this way: the display goes out and the broadcast disappears immediately after turning on or after a short period of time, the broadcast doubles, or the brightness disappears - the colors become darker. After disassembling the device, you can see a swollen or exploded capacitor on the board, and the eternal companion of this situation is a blown fuse.

Please note that after an overvoltage, it is the equipment’s power supply that breaks down first. The set of diagnostic procedures completely repeats the instructions from the previous section. As in that case, electronics repairs should be entrusted to an experienced technician so as not to harm the device or completely break it.

Matrix cable

The main signs by which it can be determined that the cause of the plasma malfunction was a broken matrix cable are the following situations:

1. The picture on the TV periodically disappears.
2. The equipment stopped showing a normal picture - ripples and interference appeared.
3. Display distortions appeared: the screen began to streak or duplicate in any geometric order.

After contacting service centers, there are two options for the development of events:

• Loop repair.
• Replacement of a faulty part of a part.

The first option is eliminated due to its inexpediency and complexity, since it is much easier to dismantle the breakdown and replace it with a working part than to try to repair the LG equipment. It is strictly not recommended to carry out any manipulations on your own.

Backlight

One of the most popular reasons why this problem occurs is when the screen backlight does not work. In LV technology, failure of LEDs in LED backlighting is far from uncommon. This is determined quite simply - if the picture “blinks” and ripples, then the root of the evil lies in the faulty illumination of the polymer liquid crystal layer.

It is almost impossible to repair such a problem at home, if only because of the lack of necessary parts - ordering them from an official distributor is expensive and time-consuming, and, unfortunately, such components are not supplied to the radio market. Therefore, the best option to repair the equipment is to send it to a certified service center.

The inverter burned out

It is impossible to describe all possible malfunctions with the voltage inverter in an LCD device.

Symptoms:

1. The image flickers and becomes distorted.
2. The video appears for a long time or does not appear at all.
3. After startup, the device’s display dims and goes out almost instantly.
4. There is sound, but the screen ripples.
5. The broadcast appears blurry or so dark that it is impossible to make out what is happening.

This module is responsible for supplying energy to the backlight lamps, in addition to:

• Converts 12 volts DC voltage to high voltage AC;
• Stabilizes the lamp input current to the required values;
• Adjusts the brightness of the backlight;
• Matches the output stage of the inverter with the input resistance of the lamps;
• Protects electronic boards from short circuits and possible overloads.

After a careful external examination and diagnosis of a broken inverter, it can be repaired by someone who knows how to handle a soldering iron, a multimeter and has basic knowledge of physics and electronics. It is difficult to say exactly where these parts most often burn out, since the problem can appear anywhere: in lamps, transformers, “switches” or controllers on the board.

power unit

If there is sound on the LGI TV, but there is no picture, and the picture constantly jerks, becomes dim, is displayed incorrectly, or appears on the display late, the problem is a faulty power supply.

It is strictly not recommended to carry out manipulations without experience in repairs and knowledge of electronics. It’s better to pay money and call a teleworker who can quickly diagnose the problem and fix it.

But you can carry out an initial inspection to detect problems yourself:

• Discharge the capacitors - remove the plug from the socket (for the desperate - short-circuit it with any conductor). Open the back cover, check the cables for kinks and breaks, and check the functionality of the buttons and fuse.
• Inspect the power supply for swollen or melted capacitors or resistors. If there are any, they should be replaced.
• Measure the voltage of the output circuits of the power supply. The values ​​must match the numbers indicated in the documentation or on the board.
• If the voltage is different and reaches a value of approximately 200V, it is necessary to look for the cause of the malfunction in the primary circuit.
• If the TV reacts when you tap, the video flickers or the colors change, the source of the problem is poor soldering of modules or wires, and this is what needs to be repaired.

Ask a question to a virtual expert

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Conclusion

This article described all possible situations and reasons when there is no image on an LG LCD TV. If on plasma equipment there is sound without a picture, channels on the TV are not displayed, the screen has darkened, only the logo lights up, or it is impossible to watch movies, then the problem most likely lies in a problem with the hardware component. To diagnose and purchase components for repair, you should contact company representatives who assemble LG devices or repair points.

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