Technical Training Part 1: LCD Television

Welcome to the HDRepair Technical Training. This training module will cover the basic theories, techniques, and requirements necessary to

successfully repair a modern LCD television. Information covered in this training will be based on Vizio’s Current LCD model lineup as of

November 2010. Units being serviced in the field will consist LCD and LED flat screen televisions in the 32” to 70”

sizes. Basic Information about the new Via (internet capable) models will also be covered. Any questions, comments, or concerns you may have regarding the information in this document

may be addressed with your trainer or the Technical Support Department. On behalf of the HDRepair staff. Thank You, and we look forward to assisting you in your

continued efforts.

IntroductionIntroduction

Flat panel displays, or more commonly called LCD’s are the latest and greatest offerings in the home entertainment industry. They have been used for years in the portable and notebook computing markets, but recent developments have increased performance and size while reducing costs making them viable in the home entertainment environment. LCD displays are light weight, extremely thin and use much less power than CRT and Plasma based displays.

IntroductionFlat Panel Technology

The key to the success of the color LCD flat panel television was the discovery of Liquid Crystal.

Liquid crystal was discovered by the Austrian botanist named Fredreich Rheinizer in 1888. Liquid crystal is an unusual organic material and it is neither solid nor liquid. That means although it is liquid in form and appearance, Liquid Crystal exhibits a crystalline molecular structure that resembles a solid. Liquid crystals are rod-shaped molecules whose molecules can be aligned per cicely when subject to electrical fields. As a liquid they are able to flow over and around small groves and can change there position depending on applied voltage. When properly aligned, the liquid crystals allow light to pass through making the desired image appear.

IntroductionFlat Panel Technology

An LCD panel consists of nine layers. A florescent backlight/diffuser, a vertical polarizing filter, rear glass plate, sub pixel electrodes, A layer of liquid crystal solution, color filter, front glass plate, a horizontal polarizing filter, and a protective front plate.

How it WorksLCD Layers

A light source provided by an array of florescent or LED light bulbs, known as the backlight, makes up the rearmost layer of the LCD panel. Light is reflected from behind the panels. This light passes through the first two polarizing filters. The polarized light then passes through a layer that contains thousands of liquid crystal blobs arrayed in tiny containers called cells. The cells are, in turn arrayed in rows across the screen: one or more cells make up a pixel (the smallest discernable dot on a display). Electric leads around the edge of the LCD create an electronic field that twist the crystal molecules, which lines the light up with the second polarizing filter and allows it to pass through. Each crystal either allows light to pass through or block the light. The configuration of the crystals forms the image

LCD TV’s use the most advanced type of LCD panel known as a (TFT) display. TFT stands for thin film transistor (or active matrix) produces color images that are as sharp as traditional CRT displays. TFTs are tint switching transistors and capacitors. The three elements provide the red, green and blue light sources for each pixel that your eye perceives. They are arranged in a matrix on a glass substrate. To address a particular pixel, the row is switched on and then a charge is sent down the correct column. Since all of the other rows that the column intersects are turned off, only the capacitor at the designated pixel receives a charge. The capacitor is able to hold a charge until the next refresh cycle, and by controlling the amount of voltage supplied to the crystal , we can make it untwist only enough to allow some light through. This means that the switching occurs right at the cell turning the white light on or off and the result is faster response time.

How it WorksLCD TFT

When red, green, and blue elements are all off, white light shines through the three elements, and the pixel appears white. If the red, green and blue elements are all on, all the light is blocked and the pixel appears black.

How it WorksLCD TFT

There are may variations of the technologies used to provide the backlight in a modern LCD TV. The most common of these technologies is CCFL(Cold Cathode Florescent Light) and LED (Light Emitting Diode).

CCFL backlighting has been the standard transport used to deliver the backlighting for most of the LCD TVs in production. CCFLs are powered by a high voltage AC current, as much as 15,000volts. This current is generally produced by an inversion circuit inside the TV.

LED backlighting is a technology recently adopted by the LCD TV market. LEDs offer comparable lumens (brightness) while lowering energy consumption by up to 50%. LEDs also allow the backlight to be adjusted locally as to allow a higher contrast ratio.

How it WorksLCD Backlight

TVs being serviced will include Plasma and LCD flat screen TVs 32” to 70” in size. TVs 42” or larger can weigh as much as 200lbs and will require an additional assistant be present for handling.

As you know, larger LCD TV’s can be heavy. With the back off, the panel in some models may not be physically attached to the cabinet front and only held in place by plastic dowels. With the back off, do not carry the set vertically, keep the face of the TV angled downward to prevent the panel from falling out. If using the stand to hold the TV for troubleshooting (recommended), hold the cabinet front in place with tape.

Be careful when removing parts and connectors, do not disconnect by pulling on the wires, pull on the actual connectors only and be mindful of connector locks. Many of the newer models use FFC (Flat Flex Cables) in place of older Molex type cables. These cables are very fragile and can be easily damage if not handled properly. Be sure to undo the connector locks before removing these cables. It is also recommended to check these cables for damage or missing metal plating during inspection.

Power screwdrivers should be used for disassembly and reassembly, only after the screws have started by hand. Many of the screw locations are soft plastic or fine thread metal locations which can easily be damaged by crossthreding.

GeneralGeneral Precautions

ESD protection is mandatory during assembly/disasemably and while handling the delicate electrical components inside the TV. Please be sure to follow proper grounding teqneques by utilizing the following equipment (wrist strap, shoe strap, ESD mat, etc).

Be sure to keep your digital camera close at hand. Your digital camera is a valuable tool for diagnosing, reporting, and repairing a TV while onsite (in case of cracked screen, video problem, to check a remote, document damage, record part numbers, etc)

Having the proper test equipment and tools are crucial to successfully and quickly diagnosing and repairing TVs in the field. Having the required equipment for servicing TVs is as important as a mechanic or carpenter having all the necessary tools for there trade. At a minimum, a good DMM, DVD Player with HMDI, Component and AV capability with the related cables, Laptop, HD pattern generator, portable scope, as well as necessary hand tools will be needed to complete every repair. Be sure to carry a high quality, current version, HDMI cable.

Cable boxes, Sat receivers, blue-ray DVD players are all known to cause issues with some Vizio models. The type and effect of these issues can vary greatly. Be sure to use your standard DVD w/HDMI to test if there is an HDMI problem.

GeneralGeneral Precautions

In the following slides we will review the basic components, functions, and test points found in the more common Vizio TVs.

We will focus primarily on two Vizio models. The first is Vizio’s SV420XVT1A and Vizio’s new Via Internet TV, the SV422XVT.

Please note that even though the information provided only covers a small group of models, the information and testing procedures can be carried over and applied to many of the Vizio and non-Vizio variants.

Good working knowledge of electronics and electrical components, as well as solid knowledge in the proper use of a multimeter will be necessary to perform diagnostic testing and repair procedures.

LCD CHASSISGeneral

LCD CHASSISSV420LFHDTV10A /Overview

1. Main Board

2. Power Supply

3. T-Con Board

4. Daughter Board

5. Master Inverter

6. Slave Inverter

7. Display Board

8. Ir Board

9. LVDS Cable

10. Audio Board

11. Speakers

12. AC Adapter

LCD CHASSISSV420LFHDTV10A /Main Board

1. Micro Processor

2. Decoder IC Chip

3. Tuner Module

4. A/V Conn

5. LVDS Conn

6. Speaker Conn

7. Ir Board Conn

8. Key Board Conn

9. LED Conn

10. Power Conn

The Main Board, also known as the System Board is essentially the “Brains” of the TV. It is primarily responsible for analog to digital video conversion and the logic control functions of the TV, as well as various other tasks.

The Main Board’s Decoder IC Chip converts the incoming analog video signals from the Component, Composite, VGA, and Tuner inputs; into a Digital LVDS signal . The LVDS signal is then passed to the T-Con Board via the LVDS Cable.

The Main Board’s Microprocessor is responsible for interpreting the logic signals from the Key Board, IR Board, and the Remote Control. The logic signals are converted from an electrical pulse to a digital signal and controls system functions like power on, power off, volume and channel scan.

The Main Board houses the analog/digital cable and ATSC tuner. The tuner is responsible for decoding cable and ATCS signals from either a cable signal or over the air antenna.

The Main Board also functions as the audio decoder and amplifier for the onboard speakers in the unit. The incoming audio signals will be processed by the onboard audio decoding chip and amplified by the built in amplifier. The signal is then passed to the units onboard speakers.

LCD CHASSISMain Board Functions

LCD CHASSISMain Board Testing

Main Board, Power Connector

PIN 1 – 5V POWER ON FOR PS PINS 2, 3, 4 – 12V RUN PINS 5 TO 9 – GROUND PINS 10 TO 12 – 5V STANDBY PIN 13 – PW DIM (VBR) ** PIN 14 – PANEL ON, ~4V ** Pin 13 sends a PWM signal to the

inverter to control the brightness of the backlight. DC range is .3V to 3V from darkest to brightest by using the Backlight adjustment in the MENU screen.

Pin 14 ramps up when the lamps light.

LCD CHASSISSV420LFHDTV10A /Power Supply

1. PWR On Relay

2. Bridge Rectifier

3. 145V/165V STB

4. 400V/165V STB

5. 200V

6. 24V

7. 12V

8. 5V

9. AC Fuse

10. AC Inlet

LCD CHASSISPower Board Functions

The Power Board, also known as the PSU or Switching Power Supply is responsible for supplying the components inside the TV with the necessary and proper voltages to make the system function properly.

The Power Board takes the standard 120volt AC supply from the wall outlet and converts it to various DC voltages. These voltages in turn supply the components inside the TV such as the Main Board and Inverter Board with the correct operating voltages based on the voltage and amperage requirements for the circuits on each of the individual boards.

The makeup of a Switching Power Supply is much more complex and energy efficient than that of a more common Linier Power Supply that is generally used to power smaller devices such as a cell phone. The Switching Power Supply uses a series of transistor switches and a closed feedback loop to produce DC output that is properly regulated regardless of the load placed on the circuit.

The Power Board on this unit supplies regulated +5volts standby, +5volts, +12volts, and a separate +24 volts supply for the external CCFL circuitry. With the exception of the +5volt standby supply, the power board is switched on/off from a signal supplied by the Main Board making the unit more energy efficient when powered off.

LCD CHASSISPower Supply Testing

Remove AC then the 3 cables from the Inverters and Main Board, not the power board. This gives you protection.

Insert a 1K resistor in the female connector of J7 between pin 1 and 11. Apply AC and measure your voltages at the connectors. If a problem, troubleshoot the PS, if not, remove AC and install J7 on the Main PCB and test. If good, remove AC and connect Inverter A, apply AC and test, if not the problem, remove AC, connect Inverter B then test.

If the Main Board is suspect, reconnect the cables for the Inverters to the PS. Disconnect J7 from the Main Board, install the 1K jumper from pin 1 to pin 11 then add a 1k resistor to between pins 10 and 14 on J7. Apply AC and backlight should light up if that circuitry is good.

LCD CHASSISSV420LFHDTV10A /T-Con Board

1. LVDS Conn

2. TFT Conn

3. Indicator LED

4. Micro Processor

5. Fuse

LCD CHASSIST-Con Board Functions

The T-Con Board, also known as the TFT Driver Board produces a series of voltages and complex, precisely timed signals to manipulate the transistors within the TFT panel. The combination of voltages with the timing signals produced by the T-Con Board is what produces the visible contrast and color patterns on the TFT panel that the human eye perceives as a continuous image.

The T-Con Board receives quadruple 12 Bit LVDS signals from the Daughter Board through the LVDS Connectors which is then it then processes into TFT Drive Signals and is in turn passed to the TFT panel through the TFT Connectors.

Without the T-Con Board or TFT Drive signals, it would not be possible to reproduce the video signals from the Main Board to a viewable image on the TFT Panel.

LCD CHASSIST-Con Board Testing

Power unit on. During initial boot sequence the LED should light up blue and then fade out indicating that the boot up sequence was successful.

While unit is powered on, +12 volts is supplied to the T-Con via LVDS cable. Check for +12 volts by testing fuse F1 for proper voltage.

If proper +12 volts is present and fuse tests ok, test the regulator circuit for proper voltage.

LCD CHASSISSV420LFHDTV10A /Daughter Board(MEMC)

1. Micro Processor

2. LVDS Conn

3. LVDS Conn

LCD CHASSISDaughter Board Functions

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LCD CHASSISDaughter Board Testing

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LCD CHASSISSV420LFHDTV10A /Inverter Board

1. Inverter Coil

2. Power Conn

3. CCFL Conn

4. Feedback IC

LCD CHASSISInverter Board Functions

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LCD CHASSISInverter Board Testing

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LCD CHASSISSV420LFHDTV10A /Display Board

1. Main Board Conn

2. Ir Board Conn

3. Power Button

4. Up/Down Buttons

5. Left/Right Buttons

6. Source Button

LCD CHASSISDisplay Board Functions

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LCD CHASSISDisplay Board Testing

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LCD CHASSISSV420LFHDTV10A /Ir Board

1. Main Board Conn

2. Ir Diode

LCD CHASSISIr Board Functions

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LCD CHASSISIr Board Testing

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LCD CHASSISSV420LFHDTV10A /LVDS Cable

1. Main Board Conn

2. Driver Board Conn

3. Ferrite Core

LCD CHASSISLVDS Cable Functions

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LCD CHASSISLVDS CableTesting

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LCD CHASSISSV420LFHDTV10A /Audio Board

1. Main Board Conn

2. Driver Board Conn

3. Ferrite Core

LCD CHASSISAudio Board Functions

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LCD CHASSISAudio Board Testing

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LCD CHASSISSV422XVT/Overview

1. Main Board

2. Power Supply

3. T-Con Board

4. Daughter Board

5. Master Inverter

6. Slave Inverter

7. Display Board

8. Ir Board

9. LVDS Cable

10. Audio Board

11. Speakers

12. AC Adapter

LCD CHASSISSV422XVT/Main Board

1. Micro Processor

2. Decoder IC Chip

3. Tuner Module

4. A/V Conn

5. LVDS Conn

6. Speaker Conn

7. Ir Board Conn

8. Key Board Conn

9. LED Conn

10. Power Conn

The Main Board, also known as the System Board is essentially the “Brains” of the TV. It is primarily responsible for analog to digital video conversion and the logic control functions of the TV, as well as various other tasks.

The Main Board’s Decoder IC Chip converts the incoming analog video signals from the Component, Composite, VGA, and Tuner inputs; into a Digital LVDS signal . The LVDS signal is then passed to the Driver Board via the LVDS Cable.

The Main Board’s Microprocessor is responsible for interpreting the logic signals from the Key Board, IR Board, and the Remote Control. The logic signals are converted from an electrical pulse to a digital signal and controls system functions like power on, power off, volume and channel scan.

The Main Board houses the analog/digital cable and ATSC tuner. The tuner is responsible for decoding cable and ATCS signals from either a cable signal or over the air antenna.

The Main Board also functions as the audio decoder and amplifier for the onboard speakers in the unit. The incoming audio signals will be processed by the onboard audio decoding chip and amplified by the built in amplifier. The signal is then passed to the units onboard speakers.

LCD CHASSISMain Board Functions

LCD CHASSISMain Board Testing

Main Board, Power Connector

PIN 1 – 5V POWER ON FOR PS PINS 2, 3, 4 – 12V RUN PINS 5 TO 9 – GROUND PINS 10 TO 12 – 5V STANDBY PIN 13 – PW DIM (VBR) ** PIN 14 – PANEL ON, ~4V ** Pin 13 sends a PWM signal to the

inverter to control the brightness of the backlight. DC range is .3V to 3V from darkest to brightest by using the Backlight adjustment in the MENU screen.

Pin 14 ramps up when the lamps light.

LCD CHASSISSV422XVT/Power Supply

1. PWR On Relay

2. Bridge Rectifier

3. 145V/165V STB

4. 400V/165V STB

5. 200V

6. 24V

7. 12V

8. 5V

9. AC Fuse

10. AC Inlet

LCD CHASSISPower Board Functions

Place Holder

LCD CHASSISPower Supply Testing

Remove AC then the 3 cables from the Inverters and Main Board, not the power board. This gives you protection.

Insert a 1K resistor in the female connector of J7 between pin 1 and 11. Apply AC and measure your voltages at the connectors. If a problem, troubleshoot the PS, if not, remove AC and install J7 on the Main PCB and test. If good, remove AC and connect Inverter A, apply AC and test, if not the problem, remove AC, connect Inverter B then test.

If the Main Board is suspect, reconnect the cables for the Inverters to the PS. Disconnect J7 from the Main Board, install the 1K jumper from pin 1 to pin 11 then add a 1k resistor to between pins 10 and 14 on J7. Apply AC and backlight should light up if that circuitry is good.

LCD CHASSISSV422XVT/T-Con Board

1. LVDS Conn

2. TFT Conn

3. Indicator LED

4. Micro Processor

LCD CHASSIST-Con Board Functions

Place Holder

LCD CHASSIST-Con Board Testing

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LCD CHASSISSV422XVT/WIFI Board

1. Micro Processor

2. LVDS Conn

3. LVDS Conn

LCD CHASSISWIFI Board Functions

Place Holder

LCD CHASSISWIFI Board Testing

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LCD CHASSISSV422XVT/Bluetooth Board

1. Inverter Coil

2. Power Conn

3. CCFL Conn

4. Feedback IC

LCD CHASSISBluetooth Board Functions

Place Holder

LCD CHASSISBluetooth Board Testing

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LCD CHASSISSV422XVT/Display Board

1. Main Board Conn

2. Ir Board Conn

3. Power Button

4. Up/Down Buttons

5. Left/Right Buttons

6. Source Button

LCD CHASSISDisplay Board Functions

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LCD CHASSISDisplay Board Testing

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LCD CHASSISSV422XVT/Ir Board

1. Main Board Conn

2. Ir Diode

LCD CHASSISIr Board Functions

Place Holder

LCD CHASSISIr Board Testing

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LCD CHASSISSV422XVT/LVDS Cable

1. Main Board Conn

2. Driver Board Conn

3. Ferrite Core

LCD CHASSISLVDS Cable Functions

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LCD CHASSISLVDS CableTesting

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TroubleshootingVideo Issues

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SummaryIntroduction

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More informationIntroduction