LCD TV DIAGRAMS
Today, the main technologies in the manufacture of displaysLCD, it'sTN+film, IPS and MVA. These technologies differ in the geometry of the surfaces, control plate and front electrode. The cheapest matrix is TN + film. It works this way: if no voltage is applied to the subpixels, the liquid crystals rotate relative to each other by 90° in horizontal plane in the space between the two plates. Since the polarization direction of the filter on the second plate makes an angle of 90° with the polarization direction of the filter on the first plate, light passes through it. And if the red, green and blue subpixels are fully illuminated, a white dot appears on the screen. Ifred, green or blue subpixel is closed - formed specific color. Despite the worst viewing angles,matrix - TN + filmhas the shortest response time among all other modernLCDmatrices, which is why such TVs are bestsellers.
Description of the TV operationLCD
A brief description of the operation of the circuits of most LCD TVs: Turning onLCDTV to a 220 V network starts a switching power supply, which begins to supply stabilized voltages to the SLT analog-digital module, usually with the following values: 3.3 V, 5 V, 12 V and 33 V. In the SLT module, the processor conducts self-diagnosis to identify faults, and when the self-diagnosis test is passed, the TV starts working in STANDBY mode.So ohn is locatedmodeenergy 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 received from the video processor via the I2C bus.
The SLT module is designed for analog digital processing of video and audio signals, processing signals from the remote control, controlling the on and off of auxiliary voltages, and controlling the brightness of lampsLCDmatrix, sound control.Analog digitalThe module contains a video processor, a video signal switch, a sound processor, a clock switch, an RGB signal switch, a horizontal and vertical sync pulse generator, a tuner and SAW filters.LCDthe matrix has a digital input with an LVDS or TTL interface, depending on its model and the matrix backlight lamp, from which high-voltage wires go to the power converter.
When the processor turns on, it begins exchanging information with the matrix via the LVDS or TTL interface, depending on the typeLCDmatrices. 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 block 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 the signalintermediate frequencyfrom the tuner passes through surfactant filters to separateintermediate frequencyvideo andintermediate frequencysound that goes to the video processor, where the signal is convertedintermediate frequencyvideo to RGB color signals. In TV mode, RGB signals are sent through a switch to the processor input. The video processor extracts from the videointermediate frequencyhorizontal and vertical sync pulses, which are supplied to the HF and VF sync pulse generators - horizontal and vertical scan.
After the shapers, the clock pulses arrive at the switch. The processor converts RGB input signals into digital code and transmits them via an LVDS or TTL interface to the matrixLCD, which already displays the video. The IF audio signal goes to the input of the sound processor, and from its outputs the audio signal of the right and left channels goes to the ULF inputs. The SLT analog-to-digital module has inputs for external audio and video signals. When the TV is turned on in video mode, the video signals are switched by the switch and are fed to the CVBS/Y input and the 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 turned on, RGB signals go directly to the inputs of the video processor. When VGA mode is selected, the RGB signals from the VGA connector are switched by the switch 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 inputs of the processor and the VGA signal is decoded and transmitted to the matrix. When the video input is switched to DVI mode, digital signals from the DVI input go directly to the corresponding inputs of the processor. It decodes the given DVI signal and transmits it to the matrix.
Here is a collection of several dozen LCD TV circuit diagrams from all major manufacturers. Almost every archive contains several variants of schemes for different models TVs. The diagrams are in the BOOKS section.
Scheme
Scheme
Scheme
The electrical circuit diagram of televisions is shown in Fig. 2. The basis of the chassis is SANYO microcircuits. This is the LC863324 (IC13) microcontroller and the LA76810 (IC11) multifunctional microcircuit (IFC, IFB, video detector, FM demodulator, synchro processor, PAL/NTSC color signal decoders) LA76810 (IC11). The SECAM signal decoder is implemented on the LA7642 chip (IC12).
A specialized chip from SHARP IR3Y26A (IC1) is used as an interface between the LA76810 video processor and the LCD panel.
The TV's power supply is powered by 12 V from an AC/DC adapter (see Table 1). It generates stabilized, galvanically isolated DC voltages to power all TV units. It consists of two units: a pulsed single-cycle converter based on a PWM controller LA7610 (IC6) that controls the A829 power switch (Q11), and a push-pull generator based on elements Q14, Q15, which powers the LCD panel backlight - Fluorescent Lamp cold cathode (CCFL).
Let's take a closer look at the electrical circuit diagram.
Radio channel
The television signal is supplied to the antenna input of the analog tuner TU1 (TDQ-3CV1). The tuner is controlled by microcontroller IC13. Range selection signals with pin. 1, 41 and 42 MKs are supplied to pins 3-5 of the tuner. The RF AGC voltage is generated by the corresponding circuit as part of the IC11 microcircuit and from its pin. 4 is supplied to pin 1 of the tuner. The tuning voltage for the tuner (0...33 V) is generated by the circuit on transistor Q6 from the 33 V voltage generated by the power supply. The circuit is controlled by a 14-bit pulse-width modulator (PWM) as part of a microcontroller (its VT output is pin 8). The digital part of the tuner is powered by 5 V (pin 6) from the power supply.
The IF signal from pin 7 of the tuner TU1 through the pre-amplifier on transistor Q4 and the bandpass filter CF1 (CF38.0) is supplied to the differential input of the IF (pin 5, 6 IC11). Further processing of the TV signal is carried out by the LA76810 multifunctional microcircuit.
The LA76810 chip performs the following functions:
- amplification and demodulation of IF image and sound signals;
- brightness signal processing;
- selection and decoding of color signals of PAL/NTSC systems (delay lines of brightness and color signals are built into the video processor);
- adjusting brightness, contrast, saturation, color tone;
- switching of video signal sources;
- generation of synchronization pulses (SI) for vertical and horizontal scans.
The pin assignments of the LA76810 chip are shown in Table 2.
Table 2. Pin assignments of the LA76810 chip
| Pin number | Signal | Description |
|---|---|---|
| 1 | AUDIO OUT | Audio output |
| 2 | FM OUT | |
| 3 | PIF AGC | External capacitor of the AGC circuit of the IF path |
| 4 | RF AGC | RF AGC signal output for tuner |
| 5 | VIF IN1 | Vertical Scan Ramp Output |
| 6 | VIF IN2 | Signal input feedback personnel scan |
| 7 | GND(IF) | "Ground" of the IF path |
| 8 | VCC (VIF) | Supply voltage 5 V |
| 9 | FM FIL | FM demodulator filter |
| 10 | AFT OUT | AFC signal output |
| 11 | DATA | I²C interface data bus |
| 12 | CLOCK | I²C interface clock bus |
| 13 | ABL | Beam current limit circuit input |
| 14 | R IN | Inputs for external RGB video signals (supply OSD video signals from the microcontroller) |
| 15 | G IN | |
| 16 | B IN | |
| 17 | BLANK IN | RGB blanking signal input |
| 18 | VCC(RGB) | Supply voltage 8 V |
| 19 | R OUT | RGB video outputs |
| 20 | G OUT | |
| 21 | B OUT | |
| 22 | SD | Detector output (to identify PTsTS reception) |
| 23 | V OUT | Output of personnel SI |
| 24 | RAMP AFC FIL | Vertical Scan Ramp Voltage Generator (RVG) Filter |
| 25 | VCC(H) | Supply voltage of the master horizontal oscillator 8 V (Ipot.=12…16 mA) |
| 26 | H AFC FIL | Line scan AFC filter |
| 27 | H OUT | Line scan trigger output |
| 28 | FBP IN | Line scan SIOX input |
| 29 | VCO IREF | External reference resistor for voltage controlled oscillator (VCO) |
| 30 | CLOCK OUT | 4.286 MHz reference output for SECAM decoder |
| 31 | VCC (CCD) | Supply voltage 5 V |
| 32 | CCD FIL | Integral delay line filter |
| 33 | GND(CCD/H) | "Earth" |
| 34 | SECAM B-Y IN | SECAM B-Y/R-Y color difference inputs |
| 35 | SECAM R-Y IN | |
| 36 | APC2 FIL | PLL2 filter |
| 37 | FSC OUT | Color System Detector Output |
| 38 | XTAL | Quartz crystal 4.43 MHz chrominance channel |
| 39 | APC1 FIL | PLL filter1 |
| 40 | SEL VIDEO OUT | Composite video output for SECAM decoder |
| 41 | GND(V/C/D) | "Earth" |
| 42 | EXT VIDEO OUT | Composite video output for low frequency output |
| 43 | VCC(V/C/D) | Supply voltage 5 V |
| 44 | INT VIDEO IN | Composite video input (for internal PTSD) |
| 45 | BLK STRETCH FIL | Black Level Enhancement Circuit Filter |
| 46 | VIDEO OUT | Composite video output |
| 47 | APC FIL | Color Scheme Filter |
| 48 | VCO COIL | Output for connecting the video detector reference circuit |
| 49 | VCO COIL | |
| 50 | VCO FIL | VCO filter |
| 51 | EXT A IN | External audio input |
| 52 | SIF OUT | Audio IF output |
| 53 | SIF APC FIL | IF audio filter |
| 54 | SIF IN | FM audio demodulator output |
After amplification and demodulation, the PCTS is removed from the pin. 46 IC11 and goes to the input of the video signal switch “internal/external” - pin. 44 IC11. External video signals V1 and V2 from the PS2 connector are supplied to the second input of the switch (pin 42) through the analog multiplexer IC10. The multiplexer is controlled from the pin. 39 microcontroller IC13. The selected video signal is processed in the brightness and color channels of the IC11 video processor and is sent to the output of the microcircuit - pin. 19-21, and from here - to the LCD panel interface, chip IC1 (IR3Y26A).
If a SECAM color system signal is received, it is processed by an external decoder on the IC12 chip (LA7642). To operate the microcircuit, the following signals are supplied to it:
- PCTS on pin. 14 IC12 with pin. 40 IC11;
- gating pulses SSC on pin. 10 IC12 with pin 28 IC11;
- reference frequency 4.43 MHz from the demodulator PLL circuit to the pin. 11 IC12 with pin. 37 IC11 (via repeater on transistor Q2);
- reference frequency for adjusting the flare filter 4.286 MHz per pin. 9 IC12 with pin. 30 IC11;
- SECAM system selection signal to pin. 12 IC12 with pin. 37 IC11 (high potential, more than 3 V).
From the output of the microcircuit (pins 6 and 7 of IC12) color difference signals are removed R-Y signals, B-Y and go to the input of the video processor - pin. 34 and 35 IC11.
The rated supply voltage of the IC 12 microcircuit (pin 15) is 7.5...8 V, the current consumption is 35...40 mA.
The IC11 microcircuit includes a synchroprocessor that produces line and frame SIs to synchronize the corresponding components of the TV. These signals are used to synchronize the LCD panel interface chip IC1. Lowercase SI are removed from the pin. 27 IC11 and through the inverter on transistor Q3 are supplied to the inputs of microcircuits IC2 and IC3. The node on the IC2 chip (4 2I-NOT elements with a CMOS structure) generates a feedback signal at the output (pin 10) for the normal functioning of the PLL circuit as part of the IC11 chip (simulates the operation of a horizontal scan CRT TV). This signal is sent to the pin. 28 IC11.
Personnel SI (pin 23 IC11) through an inverter on transistor Q19 and one of the elements of the IC2 microcircuit (input - pin 12, output - pin 11) are supplied to pin. 20 IC13 for frame synchronization of the OSD menu image.
The second node on the IC3 chip produces two clock signals from the frame SI (arrived from pin 23 of IC11) and the horizontal SI:
- the horizontal frequency signal is removed from the pin. 10 IC3 and is supplied to pin. 21 IC13 for line synchronization of the OSD menu image;
- composite sync signal (CSI + SSI), removed from the pin. 11 IC3 and is supplied to synchronize the LCD panel interface to the pin. 2 IC1.
The audio signal is also processed by IC11. The output signal of the path is fed to the input of the “internal/external” switch (included in this microcircuit). The second input of the switch (pin 51) receives an audio signal from the PS2 bass input connector. The user-selected audio signal is fed to an adjustable amplifier, and from it to the pin. 1 microcircuit. from here - to the input of the audio amplifier - pin. 3 IC201 (SC386 - analogue of LM386). This microcircuit develops an output power of 0.3 W at an 8 Ohm load, operates in the supply voltage range of 5...18 V and has a quiescent current of 4 mA. The output signal is removed from the pin. 5 IC201 and, through the coupling capacitor C63 and connector JK3, is supplied to headphones or through connector S8/S4 to the dynamic head.
The UMZCH microcircuit is powered by +12 V (pin 6) from the power source.
LCD panel interface
The interface uses a chip IC1 type IR3Y26 from SHARP - a video processor with an analog input for connecting TFT LCD panels with an analog interface. The microcircuit includes a voltage stabilizer, a synchro selector, a 2-input RGB signal switch, three video amplifiers with adjustable gain, circuits for fixing the black level in the output signals and a gamma correction circuit. The input signals of the microcircuit are RGB signals to the pin. 9, 8, 6 and composite video signal on pin. 2 (on this chassis a composite clock signal is supplied to it), and the output is RGB signals on the pin. 29, 32, 35 and sync pulses on the pin. 46, 48. The microcircuit has analog inputs (voltage control) for adjusting image parameters (pin 3, 5, 38-43), but they are not used due to the fact that all adjustments are made in the video processor of the IC11 chip. Control commands are supplied from the IC13 microcontroller via the I2C digital bus.
Microcircuit IC1 is powered from a power source with voltages of 5 V (pin 10) and 7.5 V (pin 34).
Depending on the type of LCD panel, it is connected to the main board via a 24- or 30-pin connector (S3 and S2 in Fig. 2). In addition to RGB video signals, the panel requires service signals, synchronization signals and supply voltages to operate. Service signals are generated by microcontroller IC13 - these are signals L/R (pin 36), U/D (pin 35). They are fed to pins 15 and 16 of the S3 connector (and to pins 23, 22 of S2 for other panel types). The clock signals are generated by microcircuit IC1 (see description of IR3Y26) and supplied to connectors S2 and S3. Supply voltages of 17 and -15 V are formed pulse source and through contacts 4, 5 S1 are supplied to the LCD panel.
Microcontroller
This chassis uses a SANYO microcontroller type LC863324A (IC13). It is implemented on an 8-bit core and has 24 KB of ROM and 512 bytes of RAM. It contains all the standard blocks of a television controller: oscillators (system, display and quartz, at a frequency of 32.768 kHz), interrupt circuit, timers, input/output ports, PWM, comparator, screen menu generator, I2C interface. The program recorded in the ROM of the microcircuit provides service adjustments to the TV at the stage of its production or after repair.
The operation of the microcontroller is ensured by a reset circuit (elements ZD2, Q1, C11) and non-volatile memory IC9 (24C04). The microcontroller is powered by a voltage of 5 V (pin 12) from the stabilizer IC4 (78L05). In this case, the current consumption is 30 mA in operating mode, and less than 1 mA in standby mode. The assignment of the microcontroller pins is given in Table 3.
Table 3. Pin assignments of the LC863324A microcontroller
| Pin number | Designation | Type (I - input, O - output) | Description |
|---|---|---|---|
| 1 | UHF | O | UHF band selection signal |
| 2 | 50/60 | O | Not used |
| 3 | PZOOM1 | I/O | |
| 4 | PZOOM2 | I/O | |
| 5 | VOLUME-L | I/O | |
| 6 | VOLUME-R | I/O | |
| 7 | POWER | O | Power supply control signal ( high level- inclusion) |
| 8 | VT | O | 14-bit PWM tuner frequency setting signal |
| 9 | GND | - | "Earth" |
| 10 | XTAL1 | I | 32.768 kHz crystal oscillator input |
| 11 | XTAL2 | O | Crystal oscillator output 32.768 kHz |
| 12 | VDD | - | Supply voltage 5 V |
| 13 | KEY-IN | I/O | ADC input for control panel button matrix |
| 14 | AFT-IN | I/O | Input for APCG signal |
| 15 | NC | I/O | Not used |
| 16 | NC | I/O | |
| 17 | RESET | I | Reset signal input ( low level- active) |
| 18 | FILT | - | PLL filter |
| 19 | CHROMA SECAM |
I | SECAM signal reception control input (low level - SECAM) |
| 20 | V.SYNC | I | Personnel SI input |
| 21 | H.SYNC | I | Lowercase SI input |
| 22 | R.OUT | OSD RGB output | |
| 23 | G.OUT | ||
| 24 | B.OUT | ||
| 25 | OSD-BAK | RGB OSD blanking signal output | |
| 26 | I | Not used | |
| 27 | SDA0 | I/O | I2C 0 interface (for EEPROM control) |
| 28 | SCL0 | O | |
| 29 | SDA1 | I/O | I2C interface 1 (to control IC11) |
| 30 | SCL1 | O | |
| 31 | SAFTY | I | Not used |
| 32 | S-VHS | ||
| 33 | SD | I | PCTS reception identification input |
| 34 | REM-IN | I | Signal input from photodetector of remote control commands |
| 35 | U/D | O | Timing signals for LCD panel |
| 36 | L/R | O | |
| 37 | MUTE | O | Not used |
| 38 | AV1 | O | |
| 39 | AV2 | O | |
| 40 | LNA | O | |
| 41 | V-H | Range selection signal MB2 | |
| 42 | V-L | Range selection signal MB1 |
Power supply
The power supply generates stabilized voltages of 33, 17, 12, 7, 5 and -15 V, necessary for the operation of all components of the TV. In addition to the main source, there is also a DC/AC converter to power the backlight of the LCD panel. It generates an alternating voltage of about 400...450 V from a direct voltage of 12 V at a load current of 4...6 mA.
The source operates from a 220/12 V AC/DC adapter and is a DC/DC converter built on the basis of a PWM controller type 7610 (IC6). The microcircuit works in wide range supply voltages (3.6...32 V) and clock frequencies (5...350 kHz), has a totem output for controlling external bipolar transistor. The assignment of the microcircuit pins is given in Table 4.
Table 4. Pin assignments of the 7610 chip
| Pin number | Designation | Description |
|---|---|---|
| 1 | IN- | Error amplifier inverse input |
| 2 | F.B. | Feedback input/error amplifier output |
| 3 | GND | General |
| 4 | OUT | Control signal output |
| 5 | V+ | Supply voltage 12 V |
| 6 | C.S. | Control input of the soft start and short circuit protection circuit |
| 7 | C.T. | External elements of the master oscillator |
| 8 | REF | 2.5V reference output |
The microcircuit implements a current control principle called “turn-on with clock”. This means that the transistor switch is turned on by a signal from internal generator, and is turned off by feedback circuit signals - the feedback voltage is removed from the divider R72 VR1 R30, connected to a secondary voltage of 5 V, and through circuit C94 R132 R53 C151 it is supplied to the feedback input - pin 2 IC6. With the values of timing elements C44 (2200 pF) and R13 (33 kOhm) indicated in the diagram, the operating frequency of the microcircuit is approximately 60 kHz. The output parameters of the microcircuit are as follows: (pin 4) - UOL=4 V, UOH=0.25 V, ISOURSE=11 mA (RL=100 kOhm). The 12 V converter supply voltage is supplied to it through a transistor switch Q16 Q17, controlled by a signal from the pin. 7 microcontroller IC13 (high potential - power on). From the secondary windings of the transformer T4 are removed impulse voltages and through half-wave rectifiers and filter circuits are supplied to the load.
The DC/AC converter for powering the backlight lamps of the LCD panel is built according to the circuit of a push-pull self-oscillator using elements Q14, Q15, T2. Like the main source, it is powered by 12 V from the AC adapter via the Q16 Q17 key. The operating frequency of the converter is determined by the inductance of the primary windings of transformer T2, the parameters of transistors Q16, Q17 and is about 50 kHz. The alternating voltage is removed from the secondary winding of transformer T2 and, through separating capacitors C7, C8 and connectors S7 and S9, is supplied to electroluminescent backlight lamps placed directly on the LCD panel.
Service mode
Turn on the TV in operating mode and close the pin on the remote control. 2 and 14 microcircuits between each other. The message "FACTORY" or "F" should appear on the screen. If the service mode does not turn on, instead of pin. 14 close pin. 2 to 13, 15 or 16. The list of service mode submenus is given in Table 5. To switch between submenus use the MENU button on the remote control. These submenus are controlled using the P+/- and V+/- buttons on the remote control. To exit service menu close the pin. 2 and 14 remote control chips or press the MENU button in the LANGUAGE OPTION submenu. The parameters of all submenus and their values, set in a specific TV model, are given in tables 5 - 13.
Table 5. List of service mode submenus
| Submenu name |
|---|
| 1. SIGNAL |
| 2. BALANCE |
| 3. GEOMETRY |
| 4. ANALOG DATA |
| 5. PICTURE |
| 6. LOGO SETTING |
| 7.SYSTEM |
| 8. FACTORY OPTION |
| 9. LANGUAGE OPTION |
| Parameter | Meaning |
|---|---|
| S.R.Y. | 7 |
| S.B.Y. | 8 |
| RF AGC | 58 |
| VCO | 63 |
| S.CNT | 8 |
| RGB-C | 50 |
| IF-FREQ | 38.00 |
| ABL GN | 2 |
| ABL SP | 2 |
| MANU. A.F.T. | OFF |
| AUTO. A.F.T. | OFF |
| Parameter | Meaning |
|---|---|
| R.CUT | 95 |
| G.CUT | 109 |
| B.CUT | 102 |
| G.DRV | 80 |
| B.DRV | 80 |
| Parameter | Meaning | |
|---|---|---|
| PAL | NTSC | |
| H.POS | 14 | 15 |
| V.POS | 5 | 4 |
| V.SIZE | 38 | 37 |
| V.LINE | 13 | 12 |
| V.S COR | 11 | 10 |
| Parameter | Meaning | ||
|---|---|---|---|
| PAL | NTSC | SECAM | |
| CONTRAST | 0 | 63 | |
| BRIGHT | 0 | 85 | |
| COLOR | 0 | 63 | |
| SHARP | 0 | 73 | 127 |
| TINT | 0 | 73 | 127 |
| Parameter | Meaning | |
|---|---|---|
| PAL AVTO | 1 | |
| NTSC 3.58 | 1 | |
| NTSC | 1 | |
| SECAM | 1 | |
| I | 1 | |
| B.G. | 1 | |
| M | 0 | |
| DK | 1 | |
| OSD-H | 9 | |
| OSD-V | 10 | |
| X-TURN | 1 | |
| Y-TURN | 1 | |
| Parameter | Meaning |
|---|---|
| TV | 1 |
| AV | 2 |
| SVHS | 0 |
| BLUE F | 1 |
| PAL ADD | 1 |
| ZOOM | 1 |
| PLL | 0 |
| 4:3 | 1 |
| 16:9 | 1 |
| 16:9L | 1 |
| 16 OCH | 1 |
| AUTO TUNE | 0 |
| Parameter | Meaning |
|---|---|
| ENGLISH | 1 |
| GERMAN | 1 |
| RUSSIA | 1 |
| ARAB | 1 |
| CHINESE | 1 |
| GAME 1 | 1 |
| GAME 2 | 1 |
In this article we will talk to you about the device CRT TVs (kinescope ), let's sort it out block diagram these devices and talk a little about the functions of this or that unit.
I would like to immediately note that the article does not pretend to be of any scientific nature, but is purely for informational purposes and is based only on personal experience. Also, there is no information about knowledge in the field of repairing any electronic products.
So, let's start with the structural diagram CRT TVs .
Shown in the figure below structural scheme very conventional and simple, but reflects the principle of operation CRT TV .
Now let’s figure out what these letters in rectangles are:
PSU is a power supply;
CU – control unit;
SSI – sync pulse selector;
SK – channel selector;
IF – intermediate frequency amplifier;
ULF – low frequency amplifier;
MC – chromaticity module;
MCR – frame scanning module (FR);
MSR – line scan module (SR);
CRT – cathode ray tube (kinescope).
The small rectangles are the deflection coils of the vertical and horizontal scanning system.
Now let's talk briefly about each block.
Power supply (PSU)
IN modern TVs are installed impulse blocks power supply (UPS).
What does this mean? This means that the primary winding of the pulse transformer, which is used in such a UPS, is powered by time-varying current pulses. The width (time) of such a pulse is regulated by a certain circuit in order to achieve constant output voltages. The power supply provides power to all other modules and units of the TV and has two operating modes - “standby” and “working”. These modes differ in the amount of energy consumption. When the TV is in “standby” mode, i.e. turned off only from the remote control, current still flows to the power supply, only in a smaller amount. Therefore, manufacturers recommend turning off the TV with the “network” button on the front panel.
Control unit (CU)
This block includes all kinds of TV control buttons (switching channels, volume, settings, etc.), an infrared sensor for controlling the TV from the remote control. This also includes memory chips and control for turning on horizontal scanning.
Clock selector (CSI)
This selector selects horizontal and vertical sync pulses from the general video signal for blocks of horizontal and vertical scans, respectively.
Channel selector (SC)
The channel selector is a sensitive receiver that is controlled by the tuning frequency using a constant voltage. The selector produces a signal that contains the PCTS (full color television signal). The PCTS is modulated at a single frequency, which does not depend on the frequency of the received IF signal (intermediate frequency).
Intermediate frequency amplifier (IFA)
This amplifier amplifies the Intermediate Frequency (IF), Intermediate Audio Frequency (IAF) signal and the PTSD selection. The amplifier consists mainly of a video detector, an intermediate frequency audio amplifier (IFA) and an audio frequency detector.
Low frequency amplifier (LF)
It simply amplifies the sound signal.
Color module (CM)
The color module decodes red, blue and green flowers and their strengthening to the desired value.
Vertical scanning module (VRM)
This module produces a sawtooth signal with a frequency of 50 Hz, necessary for vertical (vertical) scan coils.
Line scan module (MSR)
This module produces a sawtooth signal with a frequency of 15625 Hz, necessary for horizontal (horizontal) scan coils. The CP, in addition to everything else, includes a TDKS (diode-cascade line transformer), in which, by multiplying the voltage on the capacitors, it is formed high voltage for the kinescope anode. The secondary windings of TAKS are used as power supply for secondary circuits (16 V, 12 V, 6 V, etc.).
In order to be able to identify a faulty cascade based on the external manifestation of a particular TV malfunction, it is important to understand the operating principle of the TV receiver, the purpose of all cascades and their interaction. The block diagram of the TV allows you to quickly understand the functional composition of the TV by individual components and understand the order of their interaction with each other.
So, the block diagram of a TV is a simplified circuit diagram, in which, for convenience and clarity, the functional units electrical diagram TV receivers are combined into separate blocks indicating their connections with each other.
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. The structure diagram also changed accordingly. Rather, it did not change, but was supplemented with new blocks. So in color TVs there appeared additionally: a color block, a remote control block, a switching block external devices. In LCD TVs, the circuit becomes somewhat more complicated.
This circuit applies not only to semiconductor black-and-white TVs, but also to tube ones.
Color TVs
LCD TV
Here the circuit has changed even more, since digital signal processing is mainly used. For example, COFDM is orthogonal frequency division data processing with coding, widely used in television. The abbreviation LVDS is a method of transmitting signals to a matrix. Inverter - generates voltage for backlight lamps (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. With the rest, I think it’s clear.
