Breakdown of the TV power supply: self-identification, repair and troubleshooting

A distinctive feature of the breakdown 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 TV’s power supply, you must first make a competent diagnosis of the problem.

Malfunction manifestation – how to identify a breakdown of a TV unit

Whatever the breakdown of the power supply, it will certainly affect the operation of the TV. Damage to this element is primarily indicated by the following signs:

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

When the TV is turned on normally with the manifestation of various abnormalities in the sound or image, these violations are most likely caused by some other reason, and not a breakdown of the power supply. At the same time, there are some exceptions to this rule, when the problem that has arisen is somehow connected precisely 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 picture display and sound reproduction appear only after repeated switching on and off of the TV;
• the appearance of stripes , background sound, broken image is observed .

The main causes of breakdown

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

1. Voltage drops in the network (receipt of a strongly reduced or increased output voltage). As a result of the constantly jumping voltage, not only the operation of the TV deteriorates, but also the component parts become unusable. To avoid problems due to unstable voltage, it is recommended to use a stabilizer.
2. Short circuit . It can burn out many components and components of the device, including the power supply.
3. Failure of the mains fuse . A burnt-out element will be first of all reported by the standby indicator – it will not light up.
4. Damage to capacitors . A common problem, especially with prolonged use of the TV. The deterioration of the capacitor is influenced more by temporary than external factors. The failure of this element can be recognized by visual diagnostics by its characteristic swelling (bulge).

The occurrence of faults in the power supply is also contributed by:

• non-observance of operating recommendations;
• violation of the climatic 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 winter and brought it into a heated room, do not turn on the device immediately to avoid condensation formation 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 breakdown of the power supply, you need to take several step-by-step actions.

Tv disassembly

Determining the cause of the problem begins with disassembling the device. To do this, unscrew the screws 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 metal casing.

In some TV models, additional protection can 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.

Getting to know the power supply

To take further actions, you must clearly understand what the components of the TV’s power supply look like. All modern models have more than one power supply unit. They are usually located 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. Duty power supply unit . Its main function is to keep the TV on standby and await further commands. The presence in this mode is indicated by a lighted LED indicator. For normal operation, there must be a voltage of 5V, the supply of which to the TV is provided by the watchdog element.
2. Inverter block . The main function is to provide the processor with power. If this function is disrupted, when you try to turn on the TV, it will instantly go into sleep mode. This occurs as a result of 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 power factor correction, which is reactive and active. The first is necessary for the operability of the TV, at the same time it can significantly increase the consumption of electricity and affect the rapid wear of the capacitors, which negatively affects the service life of the power supply as a whole. Active power carries out useful action, and reactive power only transfers to the load from the generator and again 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

Identifying the problem

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 is completely absent, the problem is most likely the 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 are filter capacitors, which lose their nominal properties faster than others. In this case, the damaged element does not always have visible damage. Poor filtration leads to inoperability of the power supply, failure of the inverter, software failures of the microcircuits on the board. If the capacitors are ok, check the fuse.For this purpose, a ringing is used, which will reveal 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 if the resistors have the following deviations:

• darkening;
• cracks;
• poor soldering of the conclusions;
• breakdowns 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 fault will be indicated by zero resistance.

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

Power supplies of modern TVs, as a rule, have a typical circuit. The differences are limited only to the size of the electronic components and the output power. In this regard, diagnostics and repairs are carried out according to the same method. Typical power supply diagram of a foreign TV:

Required tools and materials

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

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

When starting to repair the TV’s power supply, you must have a schematic diagram of the model at hand (if there is none, you can download it on the Internet on the manufacturer’s official website).

Step-by-step instructions for troubleshooting a power supply

Following the sequence of the check and troubleshooting scheme, you can detect and repair the main damage to the TV’s power supply:

1. We check the power cord, outlet and / or extension cord for damage.
2. We disassemble the TV and free the electronic board.
3. We examine the power supply boards, revealing if there are swollen capacitors, burst 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 consistently test fuses, diodes, electrolytic transistors and capacitors. However, it is possible to establish a breakdown of the control microcircuits only indirectly – when there is no power supply, and all discrete elements are in good order. In practice, it happens that when the power supply 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, or a burnout (breakdown) of the rectifier diodes.
7. Having identified the damaged element, we replace it.
8. If a malfunction is diagnosed when the TV heats up, it can be eliminated by cooling the defective element with a cotton swab dipped in alcohol or acetone. If it is not known which specific part is the cause, you can provoke a malfunction by heating one or another element with a soldering iron.
9. We check the repair done. We install the lamp in place of the fuse, turn on the TV to the network. If the light comes on and goes out, the indicator is on, the raster is visible on the screen, the first thing we do is measure the line scan voltage. If it is too high, we check and replace the electrolytic capacitors. The same behavior is observed when the optocouplers fail.
10. If the indicator is silent when the lamp 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 high-voltage filter. If it shows no more than 279 volts, we are looking for the cause in the broken diodes of the rectifier bridge or in a capacitor leak. If there is no voltage at all, we re-check the power circuits. You also need to test all 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 components again.

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