TV power supply failure: self-identification, repair and troubleshooting

A distinctive feature of the failure of the TV’s power supply is the complete lack of functioning of the device after connecting to the network. In this case, not only the sound and image will be absent, but also the activity indicator. To repair the power supply of the TV, you must first make a competent diagnosis of the problem.

Manifestation of a malfunction – how to identify a breakdown of the TV unit

Whatever the failure of the power supply, it will certainly affect the operation of the TV. The following signs indicate damage to this element:

• TV does not turn on
• the indicator light is off;
• the whistle of the pulse transformer is heard, while the TV does not work, as the protective device of the power supply is activated (this can also be a sign of a failure of the LED backlight).

When the TV is turned on normally with the manifestation of various deviations in sound or image, these disturbances are most likely caused by some other reason, and not by a breakdown in the power supply. At the same time, there are some exceptions to this rule when the problem that has arisen is somehow connected with the power supply:

• the indicator is on, but the TV does not start up;
• when you press the power button on the device itself, the TV does not start;
• at first, only sound appears, and only after a while – an image;
• normal display of the picture and sound playback appear only after repeated turning on and off the TV;
• there is the appearance of stripes , background sound, a broken image.

The main causes of failure

The failure of the power supply in modern LED TVs is one of the most common problems. Many factors can cause damage, but experts identify 4 main reasons:

1. Voltage fluctuations in the network (receipt of a greatly reduced or increased output voltage). As a result of constantly jumping voltage, not only the operation of the TV worsens, but the component parts also become unusable. To avoid problems due to unstable voltage, it is recommended to use a stabilizer.
2. Short circuit . It can lead to burnout of many components and parts of the device, including the power supply.
3. Mains fuse blown . The standby indicator will first of all report a burnt out element – it will not glow.
4. Capacitor damage . A common problem, especially when using the TV for a long time. The wear of the capacitor is influenced more by temporary than by external factors. The failure of this element can be recognized by visual diagnostics by its characteristic swelling (bulge).

The following also contribute to the occurrence of malfunctions of the power supply:

• non-compliance with operating recommendations;
• violation of the climate regime;
• disassembly of the device without experience and knowledge of the device.

The TV does not tolerate sudden changes in temperature and humidity. Having bought it in the winter and brought it into a heated room, do not turn on the device immediately to avoid condensation inside and premature damage to important components.

For self-repair of expensive equipment, you need to have basic technical skills and special tools. If all this is not there, it is better to immediately contact the workshop.

Diagnostics of the TV power supply before repair

To perform a competent diagnosis of a power supply failure, you need to carry out several phased actions.

TV disassembly

Determining the cause of the problem begins with disassembling the device. To do this, screws are unscrewed from the back of the TV to open access to the power side. In different TV models, the power supplies are located in different ways, so it is not always possible to immediately see this element after removing the cover. If you have just such a case, then access to the power supply is most likely closed by a protective cover made of metal.

In some TV models, additional protection may be installed specifically for the power supply. In this regard, you will have to go through several stages of unscrewing the screws that fix the desired part.

Familiarization with the power supply device

To perform further actions, it is necessary to clearly understand how the components of the TV power supply look like. All modern models have not one power supply, but several. They are located, as a rule, in one place – the board. This board is easy to distinguish from others: in addition to capacitors and other components, it contains 3 black and yellow transformers. The TV power supply consists of the following components:

1. Standby power supply . Its main function is to maintain the TV in standby mode and wait for subsequent commands. This mode is indicated by a lit LED indicator. For normal operation, there must be a voltage of 5V, the supply of which to the TV is provided by the duty element.
2. Inverter block . The main function is to provide power to the processor. If this function is violated, when you try to turn on the TV, you will experience an instant transition to sleep mode. This is due to the fact that the processor, without receiving confirmation of functionality from the inverter, stops the activation of further actions and returns to standby mode.
3. PFC block . The main task of this component is to correct the power factor, which is reactive and active. The first is necessary for the TV to work, at the same time it can significantly increase power consumption and affect the rapid wear of capacitors, which negatively affects the life of the power supply as a whole. Active power performs a useful action, and reactive power only transfers to the load from the generator and back to the generator.

Important about power supplies: https://youtu.be/vH8Nv1pZu8k The device of the TV power supply and its main components is described in this video: https://www.youtube.com/watch?v=p3YTt9Cb3Kk

Troubleshooting

Having familiarized yourself with the constituent components of the device, proceed to its diagnosis. Using a tester, ring the output of the standby power supply – the result should be 5V. If the voltage is less than this indicator or completely absent, the problem is most likely failed capacitors. To determine this, a simple inspection of these parts is enough – they will be convex. The most vulnerable components of TV power supplies include filter capacitors, which lose their nominal properties faster than others. In this case, the damaged element does not always have visible damage. Poor filtering leads to inoperability of the power supply, failure of the inverter, software failures in the microcircuits on the board. If the capacitors are OK, check the fuse. For this purpose, a ringing is used, which will detect the presence or absence of a short circuit. You should also test the board from the back side, for which you must first remove the element from the frame. Check for the following deviations on the resistors:

• darkening;
• cracks;
• poor soldering of conclusions;
• gaps between tracks.

All this can be tested visually, and then decide how to solve the problem. If the inspection shows nothing, check the resistors with a multimeter. A failure will be indicated by zero resistance.

Step-by-step instructions for repairing a TV power supply

The power supplies of modern TVs have, as a rule, a typical circuit. The existing differences come down only to the size of the electronic components and the output power. In this regard, diagnostics and repair occur according to the same method. Typical power supply circuit of a foreign TV:

Necessary tools and materials

For repairs, you should stock up on tools and materials, without which it will not be possible to eliminate the malfunction qualitatively:

• soldering iron with adjustable power;
• solder, alcohol (refined gasoline), flux;
• solder remover;
• screwdrivers in a set;
• wire cutters (side cutters);
• tweezers;
• tester (multimeter);
• lamp 100 watts.

Starting the repair of the TV power supply, you must have a schematic diagram of the model on hand (in the absence of one, you can download it on the Internet on the official website of the manufacturer).

Step-by-step instructions for troubleshooting the power supply

By following the sequence of the troubleshooting scheme, you can detect and repair the main damage to the TV power supply:

1. We check the power cord, socket and / or extension cord for damage.
2. We disassemble the TV and release the electronic board.
3. We inspect the power supply boards, revealing whether there are swollen capacitors, bursting cases, charred resistors.
4. We check the soldering, especially the soldering of the contacts of the pulse transformer.
5. If it was not possible to visually identify the damaged element, we sequentially test fuses, diodes, electrolytic transistors and capacitors. However, it is possible to establish a breakdown of control microcircuits only indirectly – when there is no power, and all discrete elements are in good order. In practice, it happens that when the power module is not working, the fuse remains intact. Such a circumstance may indicate a problem with the transistor of the high-frequency pulse generator.
6. We check, without soldering from the board, whether there is a break in the ballast resistance, a short circuit of the high-voltage filter capacitor, burnout (breakdown) of the rectifier diodes.
7. Having identified the damaged element, we replace it.
8. If a malfunction is diagnosed when the TV is heated, it can be eliminated by cooling the defective element with a cotton swab dipped in alcohol or acetone. If it is not known which particular part is the cause, a malfunction can be provoked by heating one or another element with a soldering iron.
9. We are reviewing the repairs. We install the lamp in place of the fuse, turn on the TV in the network. If the lamp lights up and goes out, the indicator is on, the raster is visible on the screen, the first thing we do is measure the horizontal scanning voltage. If it is too high, check and replace the electrolytic capacitors. The same behavior is observed in the event of failure of optocoupler pairs.
10. If the indicator is silent when the light flashes and goes out, there is no raster, this indicates a problem with starting the pulse generator. We check the voltage level on the electrolytic capacitor of the filter of the high-voltage part. If it shows no more than 279 volts, we are looking for the cause in the broken diodes of the rectifier bridge or capacitor leakage. If there is no voltage at all, we re-check the power circuits. You also need to test all the diodes of the high voltage rectifier.
11. With a strong glow of the lamp, immediately disconnect the TV from the network. We test all electronic elements again.

Samsung UA32EH4003 TV power supply repair: https://youtu.be/uGYd3hE8Zfw How to diagnose a TV power supply failure step by step and how to repair this device is described in this training video: https://www.youtube.com/watch?v =daXMYuZ1CXg Repair of switching power supplies for TVs: https://youtu.be/yru9PNAKAkE The failure of the power supply is one of the most common causes of TV failure. Guided by step-by-step instructions, you can carry out repairs yourself. In the absence of sufficient practice and theoretical knowledge, it is better to immediately contact the repair shop to avoid more serious problems.