Xoceco LC-26HC56 Schematic

LCD TELEVISION

LC-26HC56

CONTENTS

Safety precautions………………………………………………………………………..…
Alignment instructions …………………………….…….…………………………………
Method of software upgrading……………………………………………………………..
Working principle analysis of the unit……………………………….………….………….
Block diagram…………………………………..………………………………….…………
IC block diagram………………………………………………………………………..……
Wiring diagram …………………………………………………………………………….
Troubleshooting guide ………………………………………………………………..……
Schematic diagram…………………………………………………………………………
APPENDIX-A: Assembly list
APPENDIX-B: Exploded View

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Attention: This service manual is only for service personnel to take reference with. Before

servicing please read the following points carefully.

Safety precautions

1. Instructions

Be sure to switch off the power supply before replacing or welding any components or
inserting/plugging in connection wire Anti static measures to be taken (throughout the entire
production process!):
a) Do not touch here and there by hand at will;
b) Be sure to use anti static electric iron;
c) It’s a must for the welder to wear anti static gloves.
Please refer to the detailed list before replacing components that have special safety
requirements. Do not change the specs and type at will.

2. Points for attention in servicing of LCD

2.1 Screens are different from one model to another and therefore not interchangeable. Be sure to
use the screen of the original model for replacement.

2.2 The operation voltage of LCD screen is 700-825V. Be sure to take proper measures in
protecting yourself and the machine when testing the system in the course of normal operation or
right after the power is switched off. Please do not touch the circuit or the metal part of the module
that is in operation mode. Relevant operation is possible only one minute after the power is
switched off.

2.3 Do not use any adapter that is not identical with the TV set. Otherwise it will cause fire or
damage to the set.

2.4 Never operate the set or do any installation work in bad environment such as wet bathroom,
laundry, kitchen, or nearby fire source, heating equipment and devices or exposure to sunlight etc.
Otherwise bad effect will result.

2.5 If any foreign substance such as water, liquid, metal slices or other matters happens to fall into
the module, be sure to cut the power off immediately and do not move anything on the module lest
it should cause fire or electric shock due to contact with the high voltage or short circuit.

2.6 Should there be smoke, abnormal smell or sound from the module, please shut the power off
at once. Likewise, if the screen is not working after the power is on or in the course of operation,
the power must be cut off immediately and no more operation is allowed under the same
condition.

2.7 Do not pull out or plug in the connection wire when the module is in operation or just after the
power is off because in this case relatively high voltage still remains in the capacitor of the driving
circuit. Please wait at least one minute before the pulling out or plugging in the connection wire.

2.8 When operating or installing LCD please don’t subject the LCD components to bending,
twisting or extrusion, collision lest mishap should result.

2.9 As most of the circuitry in LCD TV set is composed of CMOS integrated circuits, it’s necessary
to pay attention to anti statics. Before servicing LCD TV make sure to take anti static measure and
ensure full grounding for all the parts that have to be grounded.

2.10 There are lots of connection wires between parts behind the LCD screen. When servicing or
moving the set please take care not to touch or scratch them. Once they are damaged the screen

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would be unable to work and no way to get it repaired.
If the connection wires, connections or components fixed by the thermotropic glue need to
disengage when service, please soak the thermotropic glue into the alcohol and then pull them
out in case of dagmage.

2.11 Special care must be taken in transporting or handling it. Exquisite shock vibration may lead
to breakage of screen glass or damage to driving circuit. Therefore it must be packed in a strong
case before the transportation or handling.

2.12 For the storage make sure to put it in a place where the environment can be controlled so as
to prevent the temperature and humidity from exceeding the limits as specified in the manual. For
prolonged storage, it is necessary to house it in an anti-moisture bag and put them altogether in
one place. The ambient conditions are tabulated as follows:

Temperature Scope for operation 0 ~ +50 oC

Scope for storage -20 ~ +60 oC

Humidity Scope for operation 20% ~ 85%

Scope for storage 10% ~ 90%

2.13 Display of a fixed picture for a long time may result in appearance of picture residue on the
screen, as commonly called “ghost shadow”. The extent of the residual picture varies with the
maker of LCD screen. This phenomenon doesn’t represent failure. This “ghost shadow” may
remain in the picture for a period of time (several minutes). But when operating it please avoid
displaying still picture in high brightness for a long time.

3. Points for attention during installation

3.1 The front panel of LCD screen is of glass. When installing it please make sure to put it in
place.

3.2 For service or installation it’s necessary to use specified screw lest it should damage the
screen.

3.3 Be sure to take anti dust measures. Any foreign substance that happens to fall down between
the screen and the glass will affect the receiving and viewing effect

3.4 When dismantling or mounting the protective partition plate that is used for anti vibration and
insulation please take care to keep it in intactness so as to avoid hidden trouble.

3.5 Be sure to protect the cabinet from damage or scratch during service, dismantling or
mounting.

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Alignment instructions

1. Test equipment

PM5518 (video signal generator)
VG-848 (VGA, HDMI signal generator)
CA210 (color analyzer)
PC (write HDCP KEY)

2. Alignment flow-chart

The alignment flow-chart is shown as fig-1

Check if FLASH,VGA EDID and USB FLASH (option) is written?

Check power voltages

Factory data initialization

IF channel AFT of TV and AGC Adjustment

ADC correction of VGA, YPbPr

White balance adjustment

Fig-1 adjustment flow-chart

3. Adjustment instruction

Check if the program is written? Please refer to the software instruction (table3).

3.1 Power check
Connect all the boards according to wiring diagram. Check 5V-STB at standby, tuner 32V at
power on and backlight 24V.

3.2 Adjustment
Connect all the boards according to wiring diagram then power on and check if the display is
normal?
Method for entering factory menu: press “INPUT”, “2”, “5”, ”8” and “0” in turn to enter factory
menu; press “CH+” or “CH-” to select adjustment items and press “VOL+” or “VOL-” to adjust
value items, press “MENU” repeatedly to exit. Set AGING MODE of the factory menu to ON,
AGING MODE icon will display on the top left of the screen, now you can press “NR” button to
enter the factory menu.

Write HDCP KEY

Performance check

Preset ex-factory

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Method for software upgrading: Prepare the software upgrade program and set the software
upgrade tool correctly, press CONNECT then power on, the program will upgrade automatically.
After system prompts upgrade success, press EXIT to exit. When REALTEK appear, it means the
upgrade is complete, then restart the unit.

3.3 write HDCP KEY
Turn on the PC and set the software tool correctly, press HDCP then turn on the unit, the program
will be written automatically. It needs 5s or so and after finish, system will prompt upgrade
success.
Note: HDCP button can only be pressed one time for one unit.
The power should be off and 5V-STB disappear for 5s then start writing.

3.4 Initialization
Enter factory menu, press “CH+” or “CH-” to select adjustment items and press “VOL+” or “VOL-”
to enter the sub menu or adjust value items, adjustment items are shown in table1.

Table1 sub-menu adjustment

Items Preset Introduce

HOTEL OPT OFF ON: HOTEL OPTION of factory menu is optional

OFF: HOTEL OPTION of factory menu is not optional

BACK LIGHT 0 Software will preset the data according the type of panel

LOGO OPTION ON ON: display LOGO in no signal or turn on

OFF: no LOGO display

AGING MODE OFF OFF: power off when no signal

ON: aging mode

POWER MODE 0 0: standby 1: power on 2: memory

TEMP ADJUST→

ALL COLOR

RESET RESET Initialization (operate when EEPROM data chaos)

OFF ON: white balance of each channel auto offset based on the HDMI white

balance

0: white balance of each channel adjust the offset base separately

3.5 Adjustment for AFT voltage and AGC voltage of IF channel in TV

3.5.1 IF AFT adjustment
Enter factory menu and set IFVCO to 1, enter VCO adjustment mode, disconnect J401,

adjust L421 and let AFT voltage be 2.5V±0.1V and the test points are TP104(B face), TP105(A
face). Then set IF VCO to 0, power off the unit and solder J401. (22”: L413, TP404(B face),
TP403(A face); 26”: L412, TP404(B face), TP403(A face)).

3.5.2 IF AGC adjustment

Input 184.25MHz, 60dB RF signal for Chinese or 175.25MHz, 60dB for America, adjust RP401 to
let AGC voltage be 3.3V (3.1V minimum, 3.4V maximum), the test points are TP101(B face),
TP102(A face) and there should be no obvious snowy picture. Increase the signal to 90dB and it
should be display normally and no obvious noise. (test points of 22”, 26” are TP401(B face),
TP402(A face)).

3.6 White balance adjustment

3.6.1 white balance adjustment of HDMI

a. Input VG-848 signal to HDMI port: TIMING854 (800* 600/60Hz) and eighth-level gray

scale signal of PAT920. Use color analyzer CA210 to adjust white balance.

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b. Enter factory submenu of TEMP ADJUST, Select NORMAL color temperature (9300k),
fixed value of B OFF, adjust R OFF and G OFF, let the color coordinate of the second level be
(285±8, 293±12). Fixed value of B GAIN, adjust R GAIN and G GAIN, let the color coordinate of
the seventh level be (285±4, 293±6). Adjustment R OFF, G OFF, R GAIN and G GAIN repeatedly
until the value of the two levels gray-scale are (285, 293), then set ALL COLOR to ON.

3.6.2 VGA/YPBPR/AV white balance check and correction

a. Input VG-848 signal of VGA to VGA terminal: TIMING854(800*600/60Hz)
(PATIERN:CROSS) and auto adjust to full screen, then input PAT948 black/white signal, enter
factory menu ADC ADJ, select AUTO COLOR and the system will correct automatically, after
finish, it will return to AUTO COLOR menu. Please check the picture and data, if they are
abnormal, then the correction is failure and needs to correct again. (abnormal symptom: certain of
the data are greatly different from other data or exceed or near 1000).

Input PAT920(8 gray levels), check if the white balance is normal, if not, enter TEMP ADJUST
menu and set ALL COLOR to OFF and fine adjust according the method of 3.6.1c)

b. SD correction: input VG-848 signal of YPBPR to YPBPR terminal and input TIMING968
(480i) PAT968 color bar (see fig2), (color from left to right are white- yellow- cyan- green- purple­red- blue- black), enter ADC ADJ submenu, select AUTO COLOR the system will correct
automatically, after finish, it will return to AUTO COLOR menu. Please check the picture and data,
if they are abnormal, then the correction is failure and needs to correct again.

HD correction: input VG-848 signal of YPBPR to YPBPR terminal and input TIMING976
(720P/60Hz) PAT968 color bar (color from left to right are white- yellow- cyan- green- purple- red­blue- black), enter ADC ADJ submenu, select AUTO COLOR the system will correct automatically,
after finish, it will return to AUTO COLOR menu. Please check the picture and data, if they are
abnormal, then the correction is failure and needs to correct again.

fig2

Input PAT920(8 gray levels), check if the white balance is normal, if not, enter TEMP ADJUST
menu and set ALL COLOR to OFF and fine adjust according the method of 3.6.1c)

c. Input AV signal (PM5518, 8 gray levels, PAL for Chinese and NTSC for America) to
VIDEO1 terminal, check if the white balance is normal, if not, set ALL COLOR to OFF and fine
adjust according the method of 3.6.1c)
Note: it can’t set back to ON once ALL COLOR changes to OFF. The adjustment of other color
temperature refer to 3.6.

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4. Performance check

4.1 TV function
Enter searching menu → auto search, connect RF-TV terminal with central signal source and
check if the picture is normal, if there are channels be skipped. Check TXT and V-CHIP(for
America).

4.2 AV, YPbPr terminals
Input AV/S, YPbPr/YCbCr HD signal, check if it is normal.

4.3 VGA terminal
Insert VGA terminal, input 640X480/60Hz and other supported signal and check if the display is
normal.

4.4 HDMI terminal
Insert HDMI terminal, input 640X480/60Hz and other supported signal and check if the display is
normal. Check if HDCP is normal?

4.5 check sound channel
Check the speaker and earphone output of each channel.

4.6 other function check
Check the turn on/turn off timer, sleep timer, picture/sound mode, OSD, freeze/mute, USB(option),
MAG.G feature, etc.

4.7 presetting before ex-factory

Item Setting Item Setting Item Setting

PICTURE MODE NAUTRAL

SOUND SYSTEM DK

SOUND MODE NEWS TRANSPARENCY 2

NR WEAK OSD TIME 10 ANTENNA CATV

ZOOM FULL

5. Software instruction

No. Code No. Type Function Written

NS3 5272540001 PM25VF040

NB1 5272402002 24C02N-10SI27 VGA EDID

NU3 5272501601 S25FL016AOLMF USB program Yes

Table2 ex-factory setting

LANGUAGE English/Chinese

Table3 software instruction

before

paste

Main CPU

program

Yes 22”: N203

Yes 22”: N107

VGA/HDMI COLOR

TEMP

STANDARD

Method Note

Written with

instrument like

ALL11

26”: N501

26”: N108

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Method of software upgrading

1. Open upgrade tool “RTICE” and display the interface below:

2. Check the COM port setting of the PC and press “File” → “comm. Settings….” It will display the

interface below:

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Select COM port of your PC in “COM Port Selection”. For example, if my PC COM port is COM4, I will

select COM4 and set the others items as shown above.

3. After setting, press “CTAL+W” button of your computer and at the same time press power button

on the unit to power on. It is proved that serial ports are well connected when display “yyyyyyyyy”.

Then press “Burn in Romcode” to enter the interface below:

4. Select “bootcode” software in “Image File”, the normal name is “boot.img”, then select “Boot code”

in “Burn to” and press “TV Firmware” to display the below interface.

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