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LCD TELEVISION
LC-26HC56
CONTENTS
Safety precautions...................................................................................... 1
Alignment instructions ................................................................................ 3
Method of software upgrading....................................................................... 7
Working principle analysis of the unit...............................................................10
Block diagram.............................................................................................11
IC block diagram.........................................................................................12
Wiring diagram ........................................................................................ 15
Troubleshooting guide ................................................................................ 16
Schematic diagram.................................................................................... 21
APPENDIX-A: Assembly list
APPENDIX-B: Exploded View
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
1
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.
2
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
Write HDCP KEY
Factory data initialization
IF channel AFT of TV and AGC Adjustment
ADC correction of VGA, YPbPr
White balance adjustment
Performance check
Preset ex-factory
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.
3
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 OFF ON: white balance of each channel auto offset based on the HDMI white
ALL COLOR balance
0: white balance of each channel adjust the offset base separately
RESET RESET Initialization (operate when EEPROM data chaos)
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