EX-2K Direct-View LCD Television Chassis

Circuit Description and Troubleshooting Guide

Training Manual

MODELS: KDL22L5000 KDL26L5000 KDL32L5000 KDL32L504 KDL37L5000 Course : CTV-55

KDL32L5000

CTV-55 i

Power On ........................................................................... 12PFC Circuit ........................................................................ 12Standby Power Supply ...................................................... 12Main Switching Supply ....................................................... 12

Protection ...................................................................... 12

Chapter 4 – Inverter and Backlighting ............................. 16Overview ........................................................................ 16Operation ....................................................................... 16

Chapter 5 – Protection and Service Mode ....................... 19Protection ...................................................................... 19

Self Diagnostics History ..................................................... 21Clearing the History .............................................................. 21

Status Information .............................................................. 23

Chapter 1 – Introduction ..................................................... 1Introduction ...................................................................... 1Features .......................................................................... 1Overall Circuit Description ............................................... 1

A Board ................................................................................ 1Video Processing .................................................................... 1Power Supply .......................................................................... 1Inverter .................................................................................... 1H1 Board ................................................................................. 2H2 Board ................................................................................. 2

Circuit Board Locations ........................................................ 2

Chapter 2 – Video and Audio Processing Circuits ........... 5Video Process ................................................................. 5

RF Sources .......................................................................... 5Composite Video ................................................................. 5Component Video ................................................................ 5HDMI Inputs ......................................................................... 5PC Input ............................................................................... 5

Timing Control (TCON) board .......................................... 6Troubleshooting ............................................................... 8

No Video .............................................................................. 8Video Distortions .................................................................. 8

Troubleshooting Flowchart .............................................. 8

Chapter 3 – Power Supply ................................................ 12Overview ........................................................................ 12

Table of Contents

CTV-55 1

Chapter 1 – Introduction

IntroductionThe EX2K chassis is the first release of new models for the 2009 production year. 4 models are included in this chassis series:

• KDL22L5000• KDL26L5000• KDL32L5000 KDL33L540• KDL37L5000

The models are designated as entry-level designs for the Bravia™ direct-view LCD televisions. The LCD panel is labeled as “720p” with a native display resolution of 1366 X 768. The television is, however, able to accept video input resolutions up to 1080p 60HZ via the component, PC or HDMI inputs.

FeaturesA/V Input Sources

• 3 HDMI inputs (2 rear, 1 side)• 2 composite inputs. (Video 1 shared with component 1 input)• Y/C input on side• 2 component inputs (rear only)• PC input (15 pin D-sub)• RF input for ATSC/NTSC tuner

Automatic Contrast Enhancer (ACE): Backlight level changes with varying scene brightness to increase contrast level and reduce power consumption.Bravia® Link Compatible: Allows the connection and control of optional Bravia Link modules such as DVD players and wireless link devices.24p True Cinema™: Allows for 24 frame film content to be viewed in its original form when connected to devices able to output this format. This format can only be viewed via the HDMI inputs.

Overall Circuit DescriptionFigure 1-1 illustrates an overall block diagram of the circuits incorporated into the EX2K chassis models. 4 major circuits are included along with peripheral circuits and devices. They are described as follows:

A BoardCommon among the various models using the EX2K chassis, the A board contains most of the circuitry used by the television to process the audio and video signals. The only difference among the various models is the data which is written and stored in various locations to properly communicate with the type of LCD panel used.Audio output is available as L/R analog from RCA jacks or up to 5.1 channel surround sound via an optical jack.

Video ProcessingAll video sources, regardless of resolution are processed to a resolution of 8-bit RGB at1366 X 768 with a refresh rate of 60HZ. This processed video exits the A board as Low Voltage Differential Signaling (LVDS) where it is received by the Timing Control (TCON) board mounted on the LCD panel. All of the available input sources are mounted directly to the A board.

Power SupplyThe G2BE board receives the 120VAC input and generates the required standby and switched voltages for the other circuits in the television.

InverterThe inverter board, mounted on the left side of the LCD panel (as viewed from the rear) generates the approximately 1KV of AC voltage to operate the cold-cathode fluorescent lamps for backlighting of the LCD panel. Its operating voltage is supplied by a 24VDC source from the G2BE power supply board.

Chapter 1 - Introduction

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H1 BoardLocated on the right side of the television (as viewed from the front) this board contains the power, channel up/down, volume up/down, home (menu) and input selection buttons.

H2 BoardLocated on the lower left corner of the front bezel, this board contains the power, standby and picture off/timer LED indicators. The infrared receiver for the remote controller is also located here.

Circuit Board LocationsFigure 1-2 illustrates the locations of the circuit boards with the rear cover removed. The model in the illustration is the KDL32L5000. Circuit board location is the same in all models in this series.

Chapter 1 - Introduction

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FIGURE 1-1OVERALL BLOCK DIAGRAM

A/V DECODERVIDEO PROCESSVIDEO SWITCH

AUDIO PROCESSAUDIO AMPTV MICRO

COMPOSITE ORCOMPONENT 1

RF

VIDEO 3

COMPONENT 2

HDMI 1

DVI AUDIO

PC HD15

VIDEO 2

HDMI 2

POWER SUPPLY

SWITCHES LEDIR RX

LCD PANEL

INVERTERTCON

A

G2BEH1 H2

L

R

SIDE INPUTS

ANALOG AUDIO OUT

OPTICAL AUDIO OUT

USB2.0(SERVICE ONLY)

HDMI 3

PC AUDIO

Chapter 1 - Introduction

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FIGURE 1-2CIRCUIT BOARD LOCATIONS

A BOARD

G2BE BOARD

TCON

INVERTER

H1 BOARD

H2 BOARD

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Chapter 2 – Video and Audio Processing Circuits

Video ProcessAll sources of video to be displayed are received and processed by the A board. All signal sources are also received by IC401 regardless of their original resolution or format. The function of IC401 is to convert all input resolutions and formats to 720 progressive frame-rate at 60HZ refresh rate to conform to the native resolution of the LCD panel.The properly scaled video exits IC401 as 8-bit parallel RGB formatted digital video which has been converted to Low Voltage Differential Signaling by the internal LVDS transmitter inside IC401. The differential signal lines are sent to the TCON board via a specialized cable with each differential line carried on twisted wire pairs to minimized external noise interference.Referring to Figure 2-1, the handling of each format is as follows:

RF SourcesThe dual function tuner is capable of receiving NTSC and ATSC encoded signals. Although over-the-air NTSC will cease to broadcast in 2009, other sources of NTSC content (such as VCR’s, cable television and satellite receivers) will remain that use this format as their output.NTSC RF sources are demodulated inside the tuner and exit as composite video directly to IC401. ATSC digital sources (8VSB terrestrial and QAM cable) exit the tuner as differential IF and must be demodulated by IC7101. The demodulated digital bit stream containing the overhead and payload data packets is input to IC401 where an internal decoder decompresses and separates the audio, video and control content.

Composite VideoComposite video input 1 shares the same input jacks as the component 1 input. The composite jack is simply inserted into the Y component input and is automatically detected as such. If there are any problems with auto detection of the composite or component source this input can be changed from auto detect to manual selection by the customer in the user menu.

Video input 2 is located on the side of the unit and will accept composite or Y/C (S-video). The default is composite. If a Y/C connector is inserted a mechanical switch in the Y/C jack will notify IC401 of the input format.

Component VideoThere are 2 component inputs at the rear of the unit. As mentioned previously, component 1 serves as an input for composite video if that is what is inserted into the Y component jack.Input resolutions accepted by the component inputs range from 480i 30HZ up to 1080p 60HZ. 1080p 24HZ is not supported by the component inputs. This resolution is only supported by the HDMI inputs.

HDMI InputsThere are 3 HDMI inputs on this chassis: HDMI 1 and 3 in the rear and HDMI 2 on the side. The Consumer Electronics Control (CEC) specifications of the HDMI 1.3 standard is supported giving the customer the ability to control other devices conforming to this standard that are connected to the television via the HDMI inputs. Resolutions supported by the HDMI inputs include all ATSC resolutions including 1080p 24HZ.

PC InputThe PC input is via a VGA 15 pin D-sub connector with RGB analog input. The following resolutions are supported from a PC with these output capabilities:VGA 640 × 480 31.5KHZ X 60HZ SVGA 800 × 600 37.9KHZ X 60HZXGA 1024 × 768 48.4KHZ X 60HZWXGA 1280 × 768 47.4KHZ X 60HZ

1280 × 768 47.8KHZ X 60HZ 1360 × 768 47.7KHZ X 60HZ

Chapter 2 - Video and Audio Circuit Description

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Timing Control (TCON) board

The TCON board receives the LVDS signals from the A board. There is an LVDS receiver located inside the TCON board to convert the RGB data back to its original 8-bit parallel format.Based on timing data (also located in the LVDS transmission lines) the RGB data is allocated to the proper column drivers in sync with the row drivers to place the RGB data onto the appropriate pixels on the LCD panel.The TCON board also contains memory components to store white balance, gamma and uniformity data specific to each particular LCD panel. This data is not accessible to the service technician and is why the current policy is to consider the TCON as part of the LCD panel.

Chapter 2 - Video and Audio Circuit Description

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FIGURE 2-1VIDEO PROCESS BLOCK DIAGRAM

VIDEO 2COMPOSITE/Y/C

SIDE INPUT

COMPOSITE 1 ORCOMPONENT 1

RF

COMPONENT 2

HDMI 1

HDMI 2SIDE INPUT

HDMI 3

PC HD15

A

LCD PANEL

TCON

TUNER IC7101DEMOD

IC401MT5386

ATSCDIFF/IF

NTSC

LVDS720p/60HZ

USB 2.0(SERVICE ONLY)

Chapter 2 - Video and Audio Circuit Description

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TroubleshootingSince all of the video inputs and processing is located on the A board, failures causing a loss of video or distortions in the picture need to be isolated to the A board or the LCD panel. The combining of all video processing circuitry into 2 major components makes the troubleshooting approach to seem rather simplistic and in most cases it will be just so.As anyone who has experience servicing electronic products knows, things happen in the real world that can cause failures which do not follow the rules of the academic procedures found in this manual. Always research the latest service bulletins and/or troubleshooting tips on the Sony service website before making the service call.

No VideoIf a total loss of video occurs (including OSD graphics) the most likely course of action is to bring a replacement A board to the service location since the unit is serviced at board-level only. It is unlikely that a loss of voltage from the power supply is the cause since these voltages are monitored and the unit will likely experience a protection shutdown event rather than a no video condition. Although a failure of the backlights to turn on would certainly cause a no video condition, this too would cause the unit to shut down and indicate a failure via the self diagnostics feature. There are cases where the A board can cause a no-backlight issue without a protection shutdown but you will have brought the A board with you anyways. If the replacement A board does not resolve the issue and the backlights are lighting, the LCD panel is the only other likely culprit.The presence of OSD graphics with a no video condition certainly eliminates the LCD panel as the cause and the A board will almost certainly fix the problem.

Video DistortionsThis is, by far, the most difficult failure to troubleshoot due to the many sources that can cause it. Noise emanating from the power supply, outside interferences, video process failures and even mechanical problems in the LCD panel can cause video distortion.The up-side to display devices is that they are the most valuable tool in determining the source of the problem so long as one knows the basic theory of how they function. The Appendix section of this training manual contains a section on basic troubleshooting of LCD panel televisions. The primary objective when diagnosing no video or distortions in the video is to eliminate the LCD panel as the cause. Replacement of the LCD panel requires special authorization and, in some instances, will not be allowed due to economical reasons.

Troubleshooting FlowchartThe troubleshooting flowchart in Figure 2-2 provides guidance in isolating a loss of video or distortions in the picture.

Chapter 2 - Video and Audio Circuit Description

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FIGURE 2-2VIDEO FAILURE TROUBLESHOOTING FLOWCHART

Video Failure

Yes

No video or distorted video?

OSD graphics present?

None

Distorted

No

A Board

All inputs?Yes No

YesNo

Unplug LVDS connector at

TCON while unit is running . This may need to be done more than

once

Any flashes seen on screen?

Yes

A Board

NoLCD Panel

Backlights turning on ?

Yes

NoBacklight failure

A Board

Distortion stationary? A Board

Symentrical?Yes

LCD Panel

Lines single or multi-colored

Multi-colored

Single Color

A Board

LCD Panel

No

Chapter 2 - Video and Audio Circuit Description

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Audio ProcessAs with the video inputs, all audio sources are directly input and processed on the A board. Referring to Figure 2-3, the external analog audio signals are selected by switches within IC8101 and IC8102. The selected audio is input directly to the audio processor located within IC401 where it is converted to I2C digital format for processing. Analog audio from the tuner is received as IF and also input directly to IC401.Digital audio information is available from the demodulated ATSC tuner signal along with the 3 HDMI sources. This audio is converted by the Digital Front End processor, also located inside IC401, and sent to the audio processor where equalization and surround sound effects can be controlled.The processed audio exits IC401 as I2C audio for amplification by the class-D audio amplifier IC801. SPDIF format audio is output for use by the optical output line. Analog L/R audio is also generated by IC802 for the RCA jacks at the rear of the unit.

Chapter 2 - Video and Audio Circuit Description

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VIDEO 2Y/C_COMPOSITE

A

ATSC/NTSC TUNER

VIDEO 1COMPOSITE

COMPONENT

VIDEO 3COMPONENT

HDMI 1

PC

IC801CLASS D

AUDIO AMP

OPTICAL OUT

L/R AUDIO OUT

HDMI 2

HDMI 3

L

R

AUDIO SOURCE OPTICAL OUTPUT DIGITAL TUNER

DVD HDMI 5.1

ALL ANALOG INPUTS

NTSC TUNER

SACD VIA HDMI

DVD AUDIO VIA HDMI

5.1 OR 2CH PCM

5.1 OR 2CH PCM

2CH PCM

2CH PCM

NO OUTPUT

NO OUTPUT

OPTICAL OUTPUT TRUTH TABLE

USB2.0

ETHERNET

2CH PCM

N/A

DIGITAL FE

IC7101DEMOD

I2S

AUDIO PROCESSOR

ANALOG IF

IC8101SWITCH

HDMI 1 AUDIOIC8102

SWITCH

I2S

IC401ANALOG

IC802AMP

IF

ATSC

SPDIF

I2S

FIGURE 2-3AUDIO PROCESS BLOCK DIAGRAM

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Chapter 3 – Power Supply

OverviewThe power supply used in the EX2K chassis is a traditional switched-mode type utilizing a standby supply and switched main supply. It provides the main power for the various circuits in the television.The name of the power supply board will vary depending on the size of the display. The 22-inch model will incorporate a G board, the 26 and 32-inch a G2BE board and the 37-inch using a G4 board.

Power OnA power on high command enters CN6201-1 from the A board. The high enters inverter transistor Q6201 to turn on PH6103. The hot chassis standby 12V is switched by Q6102 to turn on the main AC relay RY6101. The standby 12V is also sent to the PFC circuit and to the main switching supply to turn it on.

PFC CircuitThe Power Factor Control circuit adds additional efficiency to the switch mode supply by bringing the current and voltage in phase to simulate a DC resistive load on the AC line. By varying the duty cycle of the pull-down on the coil (L800) the voltage exiting the PFC circuit is “boosted” to generate approximately 395 volts.Note the AC relay RY6101 has a thermistor (TH6101) across the contacts. When the unit is not powered on AC voltage flows through the thermistor, is rectified by D6301 and passes through the coil of the PFC circuit. Since the PFC circuit is not functioning the rectified voltage will be approximately 160VDC and is used by the standby power supply circuits.

Standby Power SupplyAs long as AC power is supplied to the unit the standby power supply will generate 12VDC and 3.3VDC sources. The standby 12VDC is created on the primary side of the switching transformer T6101 and will be referenced to hot ground for control of the AC relay, PFC, and main

switching supply.The standby 3.3VDC is sent to the A board to power up the microprocessor and other various circuits that must be operational at all times.

Main Switching SupplyWhen the main switching supply is turned on it provides REG12V to the A board where many other regulator circuits are used to provide operating voltages for the various circuits. The UNREG 15V source is used exclusively by the audio amplifier circuits on the A board. UNREG 24VDC is also output for exclusive use by the inverter board to generate the high voltage for the fluorescent backlights.

ProtectionCertain circuits in the power supply are monitored for over-voltage, over-current and over-temperature conditions. If one or more of these detection lines is activated the main relay RY6101 will turn off along with the PFC and main switching supply circuits. If any of these circuits are activated the main switching supply will stop and the standby LED will blink in groups of 3. The following circuits in the power supply are monitored:REG 12V and UNREG24V OVP: If one or both of these voltage lines becomes excessive the corresponding zener diode (D6204 or D6205) will fire and active the latch transistors (Q6202 or Q6203) to ground the power on command.PFC OCP and OTP: An over-current or excessive temperature condition in the PFC circuit will cause a high to be applied at the latch circuit consisting of Q6104 and Q6105. This performs the same function as the previously described latch circuit but will occur on the hot ground side of the turn-on command.

Chapter 3 - Power Supply

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FIGURE 3-1POWER SUPPLY BLOCK DIAGRAM

STBY 3.3V

STBY 12V

AC IN

AC IN

Q6201Q6102

STANDBY POWER SUPPLYIC6102T6101

PRIMARY POWER SUPPLYIC6501

Q6502 , 6503T6501

TH6101

RY6101

GND8

REG 12V11

UNREG_15V4

AU GND6

STBY 3.3V3

CN6202

TO INVERTER

D6301

F14A T

PH6103

PFCIC801Q800Q802L800

UNREG_24V1~4

GND5~6

CN6201

POWER_ON1

TO A BOARD

G2BE (26/32")REG 12V

UNREG 24V

Q6202Q6203

PFC OCP

PFC OTP

Q6104Q6105

D6204

D6205

G (22")

G4 (37")

Chapter 3 - Power Supply

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TroubleshootingPower supply failures generally fall into 3 categories which are covered below. Use of the power supply troubleshooting flowchart in Figure 3-2 and the voltage test points in Figure 3-3 will guide the technician in isolating a power supply failure.Standby Supply Failure: In this case the microprocessor located on the A board is not functioning. The set will be completely dead. The first step to take is to remove AC power for about 10 seconds and then re-apply. In a properly functioning unit, the microprocessor will send a power-on high command to the power supply for approximately 2 seconds. During this time the click of the main relay will be heard as it engages followed by another click when it releases. This is, of course, assuming that the unit was not in the power on state when the AC power was removed. In this case the unit would simply turn on.If the relay engages for about 2 seconds and then releases, this indicates a functioning standby supply and operational microprocessor. If no relay click is heard, the presence of standby 3.3V will need to be verified to eliminate the standby supply or a faulty microprocessor or power on command to the power supply.Main Switching Supply Failure: When this failure occurs, the sound of the main relay engaging is heard followed by its release within 10 seconds. The unit will usually generate a 3 blink error indication on the standby LED.Protection: If the PFC over-current or over-temperature, or the REG12V or UNREG24V over-voltage detection circuits are activated, the main relay, PFC and main switching supply will be stopped and produce the same symptoms as described for a main switching supply failure. Main switching supply failures and on-board protection activation are both remedied by replacing the power supply. There is a possibility that a situation may occur where the replacement of the power supply will not solve the problem.If there is an excessive current draw on any of the secondary voltage lines of the main switching supply, the oscillator circuit located inside IC6501 of the main switching supply will stop functioning because it has its own over-current detect circuit. In this case, replacement of the power supply

will not resolve the issue and the excessive load on one of the secondary lines (UNREG24V, UNREG15V, or REG12V) must be located to determine if the A board or inverter board are the cause.

Unit Does Not Turn On

No

YesAny Relay clicks heard?

No

No

Yes

Yes

Disconnect AC power for at least 30 seconds. Re-apply

AC power

120VAC CN6101 on

G2BE Board?

3.3VDC CN6201 -3 on G2BE Board?

CN6201 -1 onG2BE Board goes high when power button pressed ?

A Board

G2BE Board

Yes

No

No AC or Defective Power

Cord

G2BE Board

G2BE Board

FIGURE 3-2NO POWER TROUBLESHOOTING BLOCK DIAGRAM

Chapter 3 - Power Supply

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FIGURE 3-3VOLTAGE TEST POINTS

CN2021 – LAMP ERROR (NORM LOW)2 – BACKLIGHT ON (3.3V)3 – DIMMER4 - GROUND

CN4201TO H1 BOARD

CN4202TO H2

BOARD

CN802TO RIGHTSPEAKER

CN62021~4 – 24V5~8 - GROUND

CN6101AC IN

CN801TO LEFT

SPEAKER

CN62011 – POWER ON2 – AC_DET3 – STBY 3.3V4, 5 – UNREG 15V6, 7 – UNREG GROUND8~10 – REG GROUND11`13 – REG 12V

CTV-55 16

Chapter 4 – Inverter and Backlighting

OverviewThe Cold Cathode Fluorescent (CCFL) backlights for the LCD panel are powered by an inverter circuit. This circuit generates the approximately 1KVRMS of high frequency AC power to strike and maintain the ionization of the gasses inside the fluorescent lamps. The inverter circuits also function as a ballast circuit to control current levels from initial startup to steady lighting of the lamps. The inverter circuits also monitor the lamps to verify that all have been ignited and continuously lit. If one or more of the lamps fails to light the unit will shut down and blink the standby LED in groups of 6.

OperationReferring to Figure 4-1, at the time the unit is powered on, the following string of events occur to light the fluorescent lamps:IC401 on the A board sends a power on high command to CN6201-1 on the G2BE board. This engages the main relay and starts the main switching supply. 24VDC is applied to CN001 on the inverter board. During this time the microprocessor inside IC401 is performing initialization routines and turning on regulator circuits located on the A board.After approximately 5 seconds, a high command (3.3V) is applied from CN202-2 on the A board to CN001 on the inverter. This starts the oscillators and drive circuits to begin the lighting of the fluorescent lamps. The lamps are “struck” with approximately 2 to 3 times their operating voltage of 1KV AC to begin ionization of the gasses within the lamps. Once the lamps begin to draw current, the inverters function as a ballast circuit to maintain control of the current.If one or more of the lamps fail to ignite, or if either of the inverter circuits fails to operate, an error detection circuit located on the inverter board will send a high command to CN202-1 on the A board. The unit will shut down and the standby LED will blink in groups of 6.

TroubleshootingMost backlight failures will cause the unit to shutdown and generate a 6-blink error indication. Since an inverter failure or defective fluorescent lamp can cause either symptom it is import to know whether the backlights have turned on when the shutdown and error indication occurs. This is easily checked when the technician is present during the failure but a bit tricky when attempting to “triage” the repair by having the customer determine if the backlights are turning on,In most instances it is relatively easy for a technician with experience to check and see if the backlights are turning on. Ambient lighting conditions and a failure of the customer to comprehend “backlighting” may make this difficult over the phone. In these cases it is sometimes helpful to ask the customer if the screen appears to go “darker” when the unit shuts down since it is easier to observe the backlights when they turn off rather than when they first start because the sound of the main relay turning off can be a clue as to when to observe the screen for a change in brightness. The point here is to try and determine whether the backlights are turning on before the unit shuts down. If they turn on before the shutdown the LCD panel will most likely require replacement. The troubleshooting flowchart in Figure 4-2 will assist in isolating the cause of a 6-blink shutdown.IMPORTANT: If a unit is found to be turning on with no backlights, yet it is not shutting down (power LED remains steady green), do not replace the LCD panel or inverter board. There cannot be a defective backlight or inverter board without a 6-blink shutdown.Anytime the backlights do not turn on and the unit does not shut down it is usually caused by the microprocessor. A failure event occurred during initialization and the microprocessor “hangs”. One of the last output lines to go active is the backlight on command to turn on the inverter. This is why the backlights never come on and there is no self-diagnostics shutdown.

Chapter 4 - Inverter and Backlighting

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FIGURE 4-1INVERTER AND BACKLIGHTING BLOCK DIAGRAM

A

LCD PANEL

INVERTER DRIVE

CN6202

PIN 1~524VDC

G2BE

CN6201 -1

INV_ERRBACKLIGHT_ON

DIMMER

CN202123

CN001

POWER_ON1

IC401

CN201POWER_ON 13

INV_ERR (NORMALLY LOW)BACKLIGHT_ON (3.3V ON)DIMMER (PWM)

POWER_ON3.3V = ON

APPROX IKV RMS

INVERTER

INVERTER DRIVE

ERRORDETECT

OSC

Chapter 4 - Inverter and Backlighting

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FIGURE 4-2BACKLIGHT FAILURE TROUBLESHOOTING BLOCK DIAGRAM

PANELBACKLIGHT ERROR 6X

No

CN1401-3ON A BOARD GOES HIGH

(3.3v)?

YesA Board

LCD Panel

CN1401 -3ON A BOARD GOES HIGH

(3.3v)?

Backlights LightAt turn-on?

No

Yes

24VDC atCN6202 -1 on G2BE Board?

No

G1BE Board

A BoardYes

Inverter BoardYes

No

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Chapter 5 – Protection and Service Mode

ProtectionSeveral areas of the television’s circuits are monitored for failures and will cause the unit to shut down. Each protection line will indicate the failure once the unit has shut down by blinking the red standby LED on the front panel in repeating groups. The failure is also recorded into memory to provide a failure history. This failure history data can be observed in the service mode which will be covered later in this chapter. An overall block diagram of the protection circuits is illustrated in Figure 5-1.LOW B+ (3X): Virtually all of the small regulated voltages on the A board are monitored for a low-voltage condition. All of the monitored lines are connected to a common point via an or-gate array of diodes. This line is called “V_DROP_DET” on the schematic of the service manual. A loss of one or more of the monitored voltages will cause the load of that circuit to forward bias the appropriate diode causing a low on the V_DROP_DET line. This low connects to buffer Q211 and causes a low to the input of IC401. The unit will shut down and generate a 3-blink error.TCON ERROR (5X): Although labeled as a TCON error, this protect circuit actually monitors the switched 12V supply power to the TCON board. The diagnostics history page also lists this as a TCON error but it is, in fact, caused by a loss of the switched 12V on the A board and replacement of this board should rectify the problem. If replacement of the A board does not resolve the issue, it is possible that the TCON board is loading the switched 12V and this requires the replacement of the LCD panel.BACKLIGHT ERROR (6X): This error can appear if the inverter circuits fail to start or operate correctly or if one or more of the fluorescent backlights fails to start. One of the first steps to take when a 6 blink error is occurring is to observe for lighting of the backlights before the shutdown occurs. If the backlights turn on before the shutdown the LCD panel will require replacement due to a failed lamp. If the backlights never turn on, replacement of the inverter board should resolve the issue.

AUDIO ERROR (8X): Any DC voltage detected on the speaker lines will cause this circuit to shut the unit down and blink the standby LED in groups of 8. This is almost always caused by a defective audio amplifier and replacement of the A board is required.

Chapter 5 - Protection and Service Mode

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IC801AUDIO AMP

BACKLIGHT ERROR 6X

REG 12V 11CN201

1INV_ERR

CN202

IC401

5X

A

Q401SWITCH

TCON 12V

TCON POWER ERROR

LOW B+ 3X

IC2015V

IC2021V

IC2093.3VDEMIC2081.8VDDR

IC2043.3V

IC2071.25V

IC2101.2V

IC2062.5V

IC2039V

IC211TU5V

D203A

D208A

D208B

D209B

D207

D203B

D209A

D206

D214A

D214B

Q211

V_DROP_DET

SPEAKER PROTECT 8X

FIGURE 5-1PROTECTION BLOCK DIAGRAM

Chapter 5 - Protection and Service Mode

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FIGURE 5-2SERVICE MODE START PAGE

Service ModeThe service mode is entered in the traditional method of pressing the “DISPLAY”, “5”, “VOL+” and “POWER” keys on the remote commander, in sequence, while the unit is powered off. If the sequence is properly executed the service mode opening page should display as illustrated in Figure 5-2. Note that several items appear on the page. Each item can be selected by using the UP and DOWN feature of the joystick on the remote or with the volume and channel buttons on the top of the television. Most of the items in the list are set at factory default values and should not be changed. The only 2 items of concern to the service technician are the “Self Diagnostics History” and “Status Information” lines.

Self Diagnostics HistoryThe self-diagnostics history page can be selected in the service mode as illustrated in Figure 5-3. This page can also be directly accessed by pressing “DISPLAY”, “5”, “VOL -” and “POWER” on the remote commander when the unit is turned off.In this page a running count is displayed of any protect shutdown events that have occurred. This is particularly useful for determining the cause of intermittent problems. The last event registered will be highlighted in red text.

Clearing the HistoryThe diagnostics history count should always be cleared once the repair has been completed to leave a clean page for any future events that may occur. This is performed by pressing the “8” followed by the “0” key on the remote commander while viewing the page. All diagnostics event counts should reset to zero.

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FIGURE 5-3SELF-DIAGNOSTICS PAGE

LAST ERROR RECEIVED

APPEARS IN RED

ERROR COUNTRESET BY

PRESSING “8” FOLLOWED BY “0”

ON REMOTE COMMANDER

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FIGURE 5-4TUNING STATUS PAGE

Status InformationBy selecting this item the page illustrated in Figure 5-4 will appear. This feature is particularly useful for troubleshooting complaints of picture quality issues from antenna or cable sources. Important information such as the type of input selected on the television (cable or antennal), the physical channel, operating frequency and modulation type are displayed. Although Automatic Gain Control (AGC) and Signal-to-Noise Ratio numbers are displayed it is best to use the signal level disgnaostics in the customer menu as illustrated in Figure 5-5.

When viewing the customer signal diagnostics a signal strength meter along with an error count column is displayed. There should be no errors displayed and the signal level meter should read higher than 30%. The AGC level is not reliable. The SNR level is important and should display the following minimum values for reliable picture quality:8VSB: 16 or greater64QAM: 24 or greater

256 QAM: 28 or greater

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FIGURE 5-5CUSTOMER TUNING STATUS PAGE

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CTV550309 7/20/09