akira LCT-20HSST User manual

LCT TV
Service Manual

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Model No.: LCT-20HSST
Version: 1.0
MODEL:
LCT-20HSST

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Model No.: LCT-20HSST
Version: 1.0
CONTENTS
SAFE PRECAUTION .............................................................................................................................. 4
BLOCK DIAGRAM ................................................................................................................................ 5
MAIN BOARD ........................................................................................................................................ 6
FACTORY MODE ADJUSTMENT ........................................................................................................ 7
TROUBLESHOOTING ......................................................................................................................... 10
HOW TO UPDATE THE SOFTWARE ................................................................................................. 12
CIRCUIT DIAGRAM............................................................................................................................ 13
PART LIST............................................................................................................................................. 28

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Model No.: LCT-20HSST
Version: 1.0
SAFETY PRECAUTION
WARNING:
Service should not be attempted by anyone unfamiliar with the necessary precaution on this receiver.
The following are the necessary precautions to be observed before servicing this chassis.
1. When replacing a chassis in the cabinet, always be certain that all the protective devices are put
back in place, such as: non-metallic control knobs, insulating covers, shields, isolation
resistor-capacitor network etc.
2. When replacing parts or circuit boards, disconnect the power cord.
3. When replacing a high wattage resistor (oxide metal film resistor) on the circuit board, keep the
resistor 10mm (1/2in) away from circuit board.
4. Connection wires must be kept away from components with high voltage or high temperature.
5. If any fuse in this TV receiver is blown, replace it with the FUSE specified in the chassis parts list.
PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in the chassis have special safety-related characteristics.
These characteristics are often passed unnoticed by a visual inspection.
Replacement parts, which have these special safety characteristics are identified in this manual and its
supplement electrical components having such features are shaded on the schematic diagram and the
parts list.
Before replacing any of these components, read the parts list in this manual carefully. The use of
substitute replacement parts which do not have the same characteristic as specified in the parts list may
create shock, fire or other hazards.

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Model No.: LCT-20HSST
Version: 1.0
BLOCK DIAGRAM

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Model No.: LCT-20HSST
Version: 1.0
MAIN BOARD

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Model No.: LCT-20HSST
Version: 1.0
FACTORY MODE ADJUSTMENT
FACTORY MODE adjustment is a special adjustment, which is controlled by I2C BUS. The TV set has
been set at optimum mode at the factory. Except for special request, such as updating software, replacing
PANEL, MEMORY, IC etc., it is hoped not to be adjusted after produced. To conduct FACTORY
MODE's adjustment, please do it according to the following steps:
1) Press the MUTE button and the number button [2、6、6、0、7、1] on the remote controller to
enter into factory menu, adjust display, cal., stv2248 or other menu. You can use navigation
key to access them.
2) In display menu, display the basic characteristic parameter such as panel resolution, mode
table, power on time, backlight on time, software version number etc.
3) In cal. menu, display the basic characteristic parameter such as external comb filter, video
format, color space, test pattern etc. Except for special need, reset nvram item and right to OK
set item are hoped not to be adjusted.
4) In stv2248 menu, select the item you want to adjust by pressing the button “ CH+” or “CH-” and
use the "VOL+" or "VOL-" button to adjust. In this menu, you can adjust the white balance,
picture modes value, SCART Audio out value and volume middle value. And the contrast value,
AGC value and the important value vcofine, vcocoa are in the sub menu 2248 adjust.
5) In OTHER menu, select the item you want to adjust by pressing the button “ CH+”or
“CH-”such as sharpness adjust, Volume Max and Volume Min value and use the "VOL+" or
"VOL-" button to adjust.
6) Press "MENU" button on the remote controller to exit the FACTORY MODE.
Page 1: Display the different characteristic parameter according to signal source and TV set model.
Item Name Default Value Note
1 Panel 640 x 480
2 Mode table
3 Power on time
4 Backlight on time
5 Version number

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Model No.: LCT-20HSST
Version: 1.0
Page 2: Display the basic default setting according to signal source.
Item Name Default Value Note
1 External comb filter on On, off
2 Video space auto NTSC, PAL, SECAM,
NTSC Japan, Auto
RGB Only for tv, video,
s-video, RGB source
3 Color space
Ypbpr smpte240 Only for
YPbPr/YcbCR
4 Test pattern None Color bar, black, gray,
White, red, green, blue
gradient, blue gradient
Used for test in
factory
5 Calibration Useless
6 Reset nvram Used for test in
factory.
7 Right to OK setting Used for test in
factory
Page 3: Set the default value of brightness and contrast as following table.
Item Description Default Value Note
2248 contrast IC 2248 contrast value 19 0~63
2248 bright IC 2248 bright value 32 0~63
2248 vcofine IC 2248 vco fine value 0~128 Depends on
hardware
2248 vcocoa IC 2248 vco coarse value 0~15 Depends on
hardware
2248 AGC Auto gain control value 24 0~64
2248 auto vco Automatically adjust vco value
2248 manual vco Manually adjust vco value
Wb manual adj Manually adjust white balance
Wb auto adj Automatically adjust white balance Used for test in
factory
Wb state preset White balance state value Used for test in
factory
Pct mode setting Picture modes value of different source
SCRT Audio out Audio amplitude value 96 80~116
Volume Middle Middle value of volume 100 0~127

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Model No.: LCT-20HSST
Version: 1.0
Set the default value of picture mode item as following table.
Single source Pct mode status Brightness Contrast Note
Dynamic 81 80
Standard 71 70
VIDEO
Soft 60 60
Dynamic 81 69
Standard 71 59
YUV
Soft 60 49
Dynamic 60 60
Standard 50 50
RGB
Soft 50 29
Page 4: Set the default value of volume and white balance adjustment as following table.
Name Description Default Value Note
Sharpness Sharpness of TV & video picture Sofetest Normal, soft, sharp,
sharpest, softest
Pw brt max video IC PW1306 max bright for video 35 0~127
Pw cnt max video IC PW1306 max contrast for video 65 0~255
Pw cnt max yuv IC PW1306 max bright yuv 55 0~127
Pw cnt max yuv IC PW1306 max contrast for yuv 85 0~225
Pw brt max rgb IC PW1306 max bright for rgb 55 0~127
Pw cnt max rgb IC PW 1306 max contrast for rgb 85 0~255
Volume Max Volume maximum value 110 0~127
Volume Min Volume minimum value 60 0~127

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Model No.: LCT-20HSST
Version: 1.0
TROUBLESHOOTING
No picture
Can see the
PRESET menu
Check the cables from
XP312 to XP110,
XP311 to XP102
Set “black screen” in
OPTION 1 to “off”
Can see picture? OK
Change the teletext
board
(E/RSAG7.820.234A)
Can see picture? OK
IC N301 Pin3, IC N302
Pin5 (H & V SYNC
output)?
Replace N304
IC N301 Pin10, IC N302
Pin2 (H & V input)?
Replace N301 or
N302
Check IC N201 Pin 45
(8V)
Check L205, N501
Check N201, 5V supplier,
S AW, 33V supplier,
TUNER
YES YES
YES
NO
NO
NO
NOK
NOK
YES, no problem
YES, no problem
YES, no problem
NOK

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Model No.: LCT-20HSST
Version: 1.0
No sound, picture ok
IC N202
PIN24, 25
IC N202
PIN47
Check input periphery
circuit
Replace N202
Replace N202
IC N202
PIN4, 6
Check speaker and the
connector form XP203 to
speakers.
NO NO
NO
YES
YES
YES

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Model No.: LCT-20HSST
Version: 1.0
HOW TO UPDATE THE SOFTWARE
The software of LCDTV stored in a 8M bit FLASH memory IC, so it can be updated when needed.
Sometimes we have to update the software of LCDTV to solve some problems. Only the authorized
people can do the updating work.
When updating the software, we need following instruments, a computer running windows NT /windows
2000/windows XP, a debug board, a serial cord with D-sub 9 pin terminals (NOT SUPPLIED).
1) Power off the LCD TV, pull down the power cord.
2) Remove the stand and back-cover, dismount the steel shield-cover
3) Connect the computer—serial cord—debug board—LCD TV (connector XP109)
4) Running the update program (tool) to load the new software
5) Plug in the power cord, the software will be wrote into the FLASH IC.
Cautions:
The updating work will erase all the parameter such as white balance value, vco value etc. So before
you update the software, you must enter the factory mode and to write down the vco values and white
balance values. When you finish the updating work, you must restore the values to right position.

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Model No.: LCT-20HSST
Version: 1.0
CIRCUIT DIAGRAM

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Model No.: LCT-20HSST
Version: 1.0

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Model No.: LCT-20HSST
Version: 1.0

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Model No.: LCT-20HSST
Version: 1.0

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Model No.: LCT-20HSST
Version: 1.0

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Model No.: LCT-20HSST
Version: 1.0

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Model No.: LCT-20HSST
Version: 1.0

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Model No.: LCT-20HSST
Version: 1.0