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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