Fundamentally electrical circuits of foreign TVs. Books on the repair and tuning of TVs. Description of the operation of the LCD TV

The book "Foreign TVs". Video processors and color decoders of foreign color televisions. Features of repair and adjustment.

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The book "Modern TVs". This book lists more than 100 models of imported color TVs. 16 television chassis are considered. For each model, a schematic diagram is provided, a detailed description of typical malfunctions, methods for their elimination and adjustment in the service mode.

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The book "Repair of foreign TVs". This book covers more than 50 TV models trademarks JVC, LG, Panasonic, Samsung, Sharp, Toshiba. Detailed recommendations are given on troubleshooting methods, as well as adjustment in the service mode.

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Book "Modern TVs 2". This book contains more than 130 TV models of imported and domestic production. 11 chassis models were considered. Service modes of 100 TV models. Philips plasma panel diagram on FM23 AA chassis

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"1001 secrets of the telemaster" (book one) - an encyclopedia of the secrets of TV repair. The composition of the television chassis of more than 90 companies, remote controls, real faults and methods for their search and elimination. Adjustments in the service mode, fragments of schemes.

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"1001 secrets of the telemaster" (book two) - an encyclopedia of the secrets of TV repair.

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The book "TV sets of the fifth and sixth generations". The device, methods of adjustment and repair of popular models of color TV sets of famous factories of the CIS countries are described.

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The book "100 malfunctions of TVs." The 100 faults discussed in this book are selected based on real world examples. Their analysis would be incomplete without taking into account the statistics of defects in individual TV components. By taking into account the limitations imposed by the operation of the components, more efficient solutions to technical problems can be found.

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The book "From the experience of repairing budget TVs." This book discusses modern budget TVs 2005-2010. releases with significant sales volumes in the markets of the CIS countries, well-known manufacturers and brands: AKAI, AKIRA, AVEST, DIGITAL, ERISSION, EUROTECH, FUNAI, GROL, HUAZHOU, JINLIPY, JVC, OPERA, ORION, PANASONIC, POLAR, ROLSEN, SANYO , SATURN, SAMSUNG, SHARP, SHIVAKI, SITRONICS, SONY, START, TCL, TOSHIBA, VESTEL, WEST with a screen size of 10-29 inches. Most of the models under consideration are fakes under famous brands, as well as all kinds of portable LCD TVs from Chinese manufacturers with a screen diagonal of 5-7 inches.

Every novice radio amateur probably has such a situation when acquaintances, having learned that you are a radio amateur, bring you equipment and ask you to look. I just recently had such a case, relatives brought a broken TV Shivaki, and in response to the fact that this is not my specialization, they told me that repairing it in the service is unprofitable, it was planned to use the TV in the garden, and if I don’t take it, then the TV will have to be thrown away. Thus, my hands were untied and, thinking why not, I would gain experience, agreed to the repair. As electricians say, most problems can be described in one sentence:

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“There is contact where there should not be (short) and there is no contact where there should be (open).”

Of course, there are breakdowns that do not fit this rule, when in the process of work the “aging” of the part occurs and its parameters change, for example, electrolytic capacitors dry out. When I asked what happened to the TV, they said: it does not turn on. first they check the fuse. It turned out to be burned out and was replaced by me with a similar one, I turn on, as a result, another blown fuse. It will also not be superfluous to ring the power cord of the equipment before this, perhaps it does not turn on because there is a break in it.

I turned it on again by connecting a 200 W incandescent lamp instead of a fuse. I have such a lamp at home in a separate cartridge, from which there are wires with crocodile clips. This lama turns on as an indicator and a current limiter in the circuit when setting up a device powered by 220 volts. If there is a short circuit in the device, in other words, its resistance is zero, the lamp lights up, as if it was connected directly to 220 volts. If the device is in normal mode, then the lamp passes through itself the current necessary for the operation of the device, since in the cold state the resistance of the filament of the lamp is small.

Graph of the dependence of the lamp current on the voltage, using the example of lamps from lanterns

In this case, the lamp caught fire, which signaled that there was a short circuit somewhere on the TV. In such cases, I usually start looking for a malfunction from the power supply. True, in this case, I first soldered a posistor, its resistance was normal. After the diode bridge was soldered, it also turned out to be working. Next, it was the turn to check the output transistor of the power supply microcircuit, so that the parts soldered in parallel did not affect the measurement results, it was also soldered.

Transistors are checked as follows: as you know, to put it simply, a bipolar transistor is 2 diodes connected to each other, either by cathodes or anodes, and are easily called in the diode test mode by connecting either a red or black tester probe to the base, depending on the structure. The collector and emitter are touched in turn with the second probe, if the numbers approximately 800 - 900 are displayed on the tester in both cases, then the transistor is intact. True, it would not be superfluous to also check it in other directions in order to be completely sure that it is working.

At the output transistor of this microcircuit Base - Emitter - Collector all called each other shortly in all directions. The cause of the short circuit was found and eliminated by replacing the chip.

Several resistors were also checked, (turned out to be intact) and replaced just in case on the advice from the forum 3 electrolytic capacitors. In total, parts were purchased for 100 rubles. After the microcircuit, the diode bridge and the posistor were soldered into place, the TV was turned on with a 200 W lamp connected instead of a fuse. Everything worked! But there was another problem, the image was dominated by red color, which was also solved on the advice of the forum by adjusting the contour in 15 minutes.

Outcome: a working TV for 100 rubles, while the cost of repairing a TV in a TV repair shop in our city starts at 700 rubles. Good luck with your repairs! AKV.

Discuss the article REPAIR OF TV SCHEMES

LCD TV SCHEMES

To date, the main technologies in the manufacture of displaysLCD isTN+film, IPS and MVA. These technologies differ in the geometry of the surfaces, the control plate and the front electrode. The cheapest matrix in price is TN + film. It works like this: if no voltage is applied to the sub-pixels, the liquid crystals rotate 90° relative to each other in a horizontal plane in the space between the two plates. Since the direction of polarization of the filter on the second plate makes an angle of 90° with the direction of polarization of the filter on the first plate, light passes through it. And if the red, green and blue sub-pixels are fully illuminated, a white dot is formed on the screen. If ared, green or blue subpixel is closed - a certain color is formed. Despite the worst viewing angles,matrix - TN + filmhas the most little time response among all other modernLCDmatrices, so these TVs are leaders in sales.

Description of the TVLCD

A brief description of the operation of the circuits of most LCD TVs:LCDthe TV to the 220 V network starts the switching power supply, which starts to supply stabilized voltages to the SLT analog-digital module, usually of the following values: 3.3 V, 5 V, 12 V and 33 V. In the SLT module, the processor performs self-diagnostics, in order to identify faults, and when the self-diagnostic test is passed, the TV starts in STANDBY mode.So ohn ismodeenergy saving, in which only the minimum required set of circuit elements remains powered. When a command is received from the remote control remote control to the IR sensor, and then from the IR sensor, the detected command code to the input of the video processor, or when a command is received from the keyboard located on the front panel of the TV to the input of the video processor, a turn-on command is sent via the I2C bus from the video processor.

The SLT module is designed for analog-to-digital processing of video and audio signals, processing signals from the remote control, controlling auxiliary voltage on and off, controlling the brightness of lampsLCDmatrix, sound control.analog digitalthe module contains a video processor, a video signal switcher, a sound processor, a clock signal switcher, an RGB signal switcher, a horizontal and vertical sync generator, a tuner and SAW filters.LCDthe matrix has a digital input with an LVDS or TTL interface, depending on its model, and a matrix backlight, from which high-voltage wires go to the power converter.

The turned on processor starts exchanging information with the matrix via the LVDS or TTL interface, depending on the type.LCDmatrices. If the TV is turned on in TV mode, the processor sends a code corresponding to the frequency of the desired channel to the Tuner unit via the I2C bus. The tuner is tuned to the required frequency, and an intermediate frequency signal of the selected channel appears at its output. Then signalintermediate frequencyfrom the tuner passes through the SAW filters to separateintermediate frequencyvideo andintermediate frequencysound that enter the video processor, in which the signal is convertedintermediate frequencyvideo to RGB color signals. In TV mode, RGB signals are fed through the switcher to the input of the processor. Video processor extracts from videointermediate frequencyhorizontal and vertical sync pulses that are fed to the HF and VF sync pulse generators - horizontal and vertical scanning.

After the shapers, the clock pulses arrive at the switch. The processor converts the input RGB signals to a digital code and transmits them via an LVDS or TTL interface to the matrixLCD, which already displays the video. The sound signal of the IF is fed to the input of the sound processor, and from its outputs the sound signal of the right and left channels is fed to the ULF inputs. The analog-to-digital SLT module has inputs for external audio and video signals. When you turn on the TV in video mode, the video signals are switched by the switcher and fed to the CVBS / Y input and C input of the video processor, and the audio signals of the right and left channels are fed to the corresponding inputs of the sound processor.

When RGB mode is enabled, RGB signals are sent directly to the inputs of the video processor. When VGA mode is selected, the RGB signals from the VGA connector are switched by the switcher to the RGB inputs of the processor. The horizontal and vertical sync pulses from the VGA connector are switched by the switch to the corresponding processor inputs and the VGA signal is decoded and transmitted to the matrix. When the video input is set to DVI mode, digital signals from the DVI input go directly to the corresponding processor inputs. It decodes given signal DVI and transmits it to the matrix.

Here is a collection of several dozen LCD TV circuits from all major manufacturers. In almost every archive there are several options for schemes for different models TVs. The diagrams are in the BOOKS section.

Scheme

Scheme

Scheme

Scheme

Seal

In order to be able to determine the faulty cascade by the external manifestation of a particular TV malfunction, it is important to understand the principle of operation of the TV receiver, the purpose of all cascades and their interaction. Structural scheme TV allows you to quickly understand the functional composition of the TV for individual nodes and understand the order of their interaction with each other.

So, the block diagram of a TV is a simplified electrical circuit diagram, in which, for convenience and clarity, the functional units of the electrical circuit of the TV receiver are combined into separate blocks indicating their interconnections.

Over the past decades of development, television technology has undergone significant changes. From black and white TVs, then to color and finally to digital LCD and plasma panels. Accordingly, the structural scheme also changed. Rather, it did not change, but was supplemented with new blocks. So in color TVs appeared additionally: a color unit, a remote control unit, a switching unit for external devices. In LCD TVs, the scheme is somewhat more complicated.

This scheme applies not only to semiconductor black and white TVs, but also to lamp ones.

Color TVs

LCD TV

Here the circuit has changed even more, as digital signal processing is mainly used. For example, COFDM is an encoded orthogonal frequency division processing widely used in television. Abbreviation LVDS - a method of transmitting signals to the matrix. Inverter - generates voltage for backlights (or LEDs in LCD and OLED TVs) and regulates it. Flash memory (ROM) is the TV's own memory that stores information about your settings, built-in functions, and receiver control. RAM - RAM, participates in data processing during TV operation. The rest I think is clear.

Structural diagram of an LCD TV

Something similar will be on the structural diagram of a plasma TV.

On the circuit diagram for division into functional blocks, positional designations of elements of capacitors, resistors, and so on are used. For example, R805, C806 will refer to the power supply, and R705 and C706 to line scanning. The corresponding designations will also be present on the TV chassis board.