Troubleshooting - LG 47LG70YD Service Manual

1. TV/CATV doesn't display
Check TU401 Pin15(Video output),
Pin16(Sound output)
Can you see the normal signal?
YES
Check the output of TR(Q503).
Can you see the normal waveform?
YES
Check the output of Main IC(IC100).
Especially you should check
The H,V sync and clock.
Can you see the normal waveform?
YES
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 TU800 Pin 24~34
Can you see the normal signal?
YES
Check the output of Main IC(IC100).
Especially you should check
The H,V sync and clock.
Can you see the normal waveform?
YES
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.
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C
Only for training and service purposes

TROUBLESHOOTING

NO
Could you measure voltage of TU800 & IIC
lines?
Are they all normal?
You should replace TUNER.
NO
You should decide to replace TR(Q503) or not.
NO
After checking the Power of Main IC(IC100) you
should decide to replace Main IC or not.
NO
Could you measure voltage of TU800 & IIC
lines?
Are they all normal?
You should replace TUNER.
NO
After checking the Power of Main IC(IC100) you
should decide to replace Main IC or not.
- 17 -
NO You should check power line
YES
NO You should check power line
YES
& IIC lines.
& IIC lines.
LGE Internal Use Only