Troubleshooting - LG LB81D Service Manual

1. TV/CATV doesn't display
Check TU401 Pin15(Video output),
Pin16(Sound output)
Can you see the normal signal?
Check the output of TR(Q503).
Can you see the normal waveform?
Check the output of Main IC(IC100).
Especially you should check
The H,V sync and clock.
Can you see the normal waveform?
This board has big problem because Main IC(IC100)
have some troubles.
After checking thoroughly all path once again, You
should decide to replace Main Board or not.
2. DTV doesn't display
Check the output data of TU401 Pin 24~34
Can you see the normal signal?
Check the output of Main IC(IC100).
Especially you should check
The H,V sync and clock.
Can you see the normal waveform?
This board has big problem because Main IC(IC100)
have some troubles.
After checking thoroughly all path once again, You
should decide to replace Main Board or not.
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes

TROUBLESHOOTING

NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
Could you measure voltage of TU800
& IIC lines?
Are they all normal?
You should replace TUNER.
You should decide to replace TR(Q503) or not.
After checking the Power of Main IC(IC100) you
should decide to replace Main IC or not.
Could you measure voltage of TU800 & IIC
lines?
Are they all normal?
You should replace TUNER.
After checking the Power of Main IC(IC100) you
should decide to replace Main IC or not.
- 15 -
You should check power line
NO
YES
You should check power line
NO
YES
& IIC lines.
& IIC lines.
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