LG 42LA790V / 42LA790W (CHASSIS:LD34D) Service Manual ▷ View online
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Normal
audio
Y
N
Move to No
video/No audio
No video
Normal audio
Check Back Light
On with naked eye
On
Y
N
Check Power Board
12v,3.5v etc.
Normal
voltage
Y
N
Replace T-con Board
or module
And Adjust VCOM
Repair Power Board
or parts
Check Power Board 24v output
Normal
voltage
Y
Replace Inverter
or module
N
Repair Power
Board or parts
End
Always check & record S/W Version and White
Balance value before replacing the Main Board
Replace Main Board
Re-enter White Balance value
※
Precaution
Established
date
Standard Repair Process
Revised date
LCD TV
Error
symptom
A. Video error
No video/ Normal audio
☞A5
☞A1
☞A5
☞A28
☞A4 & A7
First of all, Check whether all of cables between board is inserted properly or not.
(Main B/D↔ Power B/D, LVDS Cable,Speaker Cable,IR B/D Cable,,,)
2012. 12 .06
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Normal
voltage?
Check various voltages
of Power Board
( 3.5V,12V,20V or 24V…)
No Video/
No audio
Check and
replace
MAIN B/D
Y
Replace Power
Board and repair
parts
N
End
Standard Repair Process
A. Video error
No video/ No audio
☞A5
Established
date
Revised date
LCD TV
Error
symptom
2012. 12 .06
39 / 90
A. Picture Problem
Picture broken/ Freezing
Y
N
☞ A6
N
Check RF Signal level
Normal
Signal?
Check RF Cable
Connection
1. Reconnection
2. Install Booster
Check
S/W Version
Use Signal Test
Check Signal status
S/W Upgrade
Check whether other equipments have problem or not.
(By connecting RF Cable at other equipment)
→ DVD Player ,Set-Top-Box, Different maker TV etc`
SVC
Bulletin?
Replace
Main B/D
Check
Tuner soldering
Normal
Picture?
Y
N
Y
Close
Normal
Picture?
Y
Close
. By using Digital signal level meter
. By using Diagnostics menu on OSD
( Menu→ Set up→ Support → Signal Test )
- Signal strength (Normal : over 50%)
- Signal Quality (Normal: over 50%)
Normal
Picture?
Y
Contact with signal distributor
or broadcaster (Cable or Air)
N
N
Normal
Picture?
Y
Close
N
☞ A7
Standard Repair Process
Established
date
Revised date
LCD TV
Error
symptom
2012. 12 .06
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A. Picture Problem (DVB-S/S2)
Tuning fail, Picture broken/ Freezing
Y
N
☞ A6
Check RF Signal level
Normal
Signal?
Check
S/W Version
S/W Upgrade
SVC
Bulletin?
Normal
Picture?
Y
N
Y
Close
Check RF signal cable (DVB satellite signal or not)
Check whether other equipments have problem or not.
(By connecting RF Cable at other equipment)
→ Set-Top-Box, Different maker TV etc
Y
Change satellite setting
(match with installed ANT)
N
Normal
Picture?
Y
Close
N
☞ A7
Standard Repair Process
Established
date
Revised date
LCD TV
Error
symptom
Check satellite setting.
- Check LNB frequency.
- Check satellite
- Check Satellite connection
(DiSEqC
(DiSEqC
, motor, etc…)
Normal
setting?
Contact with
signal distributor
or broadcaster
(Cable or Air)
Close
N
Check
Tuner soldering
Replace
Main B/D
2012. 12 .06
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