Why does not the TV

Reasons for failure TV found trivial and confusing. We offer to study the interior of a typical TV. Excluding digital signal decoding circuit boards from a satellite or terrestrial broadcast.

How does the TV

It took a long time as commissioned the first TVs with picture tubes, but global achievements did not happen. Except for microprocessors today to refuel all. Previously, their functions are implemented almost on lamps that take up much space. Now cascades assembled in a neat chip, new subtleties of the sound, but the main work as before.

Signal path to the reception intermediate frequency division does not detect. The image and sound are close, although different carriers, and modulation type does not match. receiver chip standing when the antenna cable:

1. Implements relevant primary sampling frequency of the incoming spectrum using a custom circuit.
2. Amplifies the received signal directly to the reception frequency, for example, 570 MHz.
3. With the internal oscillator frequency downconverts mixture (audio + video) to tens of MHz (slightly more than 30 MHz).

At the output worth frequency amplifier, RF amplifier is called, but you have to be confused with the radio frequency amplifier. The increase in the amplitude of the signal goes to high-quality filters, for example, a surface acoustic wave. The entire set is supplied to the unit amplifiers intermediate frequency of the sound and images. There are detectors. The second intermediate frequency of the sound is different, for example, 5.5 or 6.5 MHz depending on the standard. Detectors are trying to find useful information carriers, with the successful outcome of the microprocessor receives an appropriate message. Then the control signal opens the desired notch filter. Sound travels at a low frequency amplifier and output to the speakers.

There is a stereo decoding circuit, the TV must be able to recognize the video PAL and SECAM formats. In each case, on specific grounds it appears that it was activated exclusively the desired circuit.

Setting the input stages of the receiver chip has been central controller controlling the notch filters and other things. Special numerical code decoded by the receiver, and contains information on the frequency. Accordingly, the varactors are rearranged input polling circuits and the oscillator begins to produce the desired signal. Add that before demodulating the first intermediate frequency of the sound passes further transformation. In total we have two. It is necessary to pay off the mirror frequency of the channel, eventually, increase selectivity and sensitivity of the receiver. In professional radio frequency three conversions and more.

This is how the TV. Signals horizontal and vertical deflection in analog broadcasting laid directly in the signal. Now that the information is divided into frames, it is not necessary. Vertical scanning frequency is now possible to change, and the CPU is already customizes the image. Complicated algorithms. Smart Electronics is able to carry out an approximation, the behavior prediction picture and sound. Reception becomes assured quality.

If the TV does not want to be included

When the TV does not turn on, the power supply is faulty. Of course, before the repair you need to ring cord and determine the presence of voltage in the power outlet, often have to climb inside. TV power unit is designed to receive a plurality of nominal voltages generated by the secondary windings of the transformer. The small size of the core indicates that the power supply pulse.

For TVs up special IC pulse generators and keys, which implement the concept. How to deal with the power supply? It needs to get on circuitry features. For example, here: http://telemaster.ru/shema/. If you can not see TV brands, just look at what chip power supply is built. Secretly tell names are not brands, and the marking of electronic assemblies. With the card on hand is easy to find the right. If the specified name is not available, first of all through the Yandex search relies analogues (or circuit to another site).

According razdobytoy scheme begins repairs. Under the scheme it is clear where to climb to the tester, where and what voltage. It is useful to get Data Sheet (specifications) for each chip, foreigners (as opposed to the Russian producers) often supply even cheap products detailed documentation. Inside show up connection nuances.

Switching power supplies. Degaussing loop (often with PTC) is usually made solely on kinescopes, with color. The shadow mask of steel is magnetized and begins to deflect the electrons. As a result, the image becomes altered. PTC thermistor provides a gradual decrease in the demagnetizing field amplitude. Resistance of heating element from increasing. As a result, the picture on the screen is clear. By the way, if the fuse is constantly crashes on TVs with cathode-ray tube is often the case in the PTC thermistor degaussing loop and on the perimeter of the picture tube. Try to turn off the power to remove the wire around the screen (on the inside of the body). If your TV has started to work, defective posistor.

For the rest, it is recommended to move the scheme from input to output:

• Harmonic Filter of inductance, capacitance resistors.
• Diode bridge.
• high frequency pulse generator.
• Power switch with a radiator.
• Transformer.
• Rectifier diodes.
• The output of the filter.

Often the security elements used in power supplies, such as varistors, drastically reducing the resistance when the voltage, closing current to ground.

If your TV has no sound

If the sound does not work in the TV, the root of evil lies increasingly in the settings. For example, if using an HDMI home theater built-in speakers come to life, a low frequency amplifier is operational. The reason lies breakage or damage to the sound detector or one of the notch filters, or malfunction of the microprocessor. If an image is present, breakage crept not previously detector unit where the sound is converted to a second intermediate frequency. Otherwise the picture would disappear. Remains miniscule chance that the sound is cut off filters before, but the probability of such an outcome is almost zero.

Troubleshooting begins with the setting and the smooth transition to the detectors and filters. It is useful to flip through the channels of different broadcast stations. If the sound is somewhere there, breaking in the filters.

The TV screen shows nothing

When not working the TV screen, the snag is often in illumination. As for the close of the inverter. Using the conclusions of earlier claim that before the block detectors and notch filters could not fault creep. Otherwise, the sound disappears. There is an update mode in which a extinguished screen system for Internet connection requests to the server, the new firmware. Then, after the operation is completed the TV will turn off by yourself.

Other malfunctions TV

Finally, if you do not work the TV remote, the first thing checked batteries. In the second place blame button. Inside the console is worth a transmitter encoding keystrokes. Break especially nothing. In rare cases, the receiver on the TV breaks. The most common infrared radiation does not pass through objects. Try cleaning the glass covering the sensor and transmitter.

When not working on the TV, the reason most often in the combustion itself. As for the touch panels, they burn from electrical surges. Operate the equipment with care.