LG CM7420 Service Manual page 47

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NO SOUND
There is no sound output in the AUX FUNCTION, repair the set according to the fol-
lowing guide.
6-4. IN THE AUX FUNCTION
6-4-1. Solution
Please check and replace IC202 on MAIN board.
6-4-2. How to troubleshoot (Countermeasure)
1) Check AUX_L/R signals to IC202 (Pin7, 8).
2) Check if ADC_BCK, ADC_LRCK, & DAC_MCLK are entered from IC501 to IC202.
3) Check if ADC_DATA is entered from IC202 to IC501.
If no signal, check +5 V & +3.3 V(ADC) for IC202. If is NG, replace it a new one.
4) Check the following I2S signal flow from IC501 to IC602. (Refer to Item 6-1.)
If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to
the IC is distorted or no signal, replace it with a new one.
5) Check if the digital audio AMP block is okay. Refer to "Digital Audio AMP" guide on Item 6-3.
If AMP is damaged, replace it with a new one.
6-4-3. Service hint (Any picture / Remark)
AUX_L/R
IC202
CS5346
DAC_MCLK
ADC_DATA
IC501
DAC_LRCK
MLC3700
DAC_DATA
DAC_MCLK
IC801
BEAT_DATA
FS503B
BEAT BOX
< AUX function signal fl ow >
ONE POINT REPAIR GUIDE
AUX
DAC_BCK
AMP IC
IC602
TAS5631
PS9854
PWM
< Signal check point >
3-28

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