LG OK75 - Troubleshooting: No Sound (Portable Function)

3-19
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Only for training and service purposes.
< MAIN board bottom view >
IC301
IC301
NO SOUND
There is no sound output in the PORTABLE Function, repair the set according to the following guide.
6-6. PORTABLE FUNCTION,
6-6-1. Solution
Replace IC301 on MAIN board.
6-6-2. How to troubleshoot (Countermeasure)
1) Check if PT_LR signals to IC301 (pin29, 30).
2) Check if DSPI_BCK, LRCK, MCLK are entered from IC501 to IC301.
3) Check if ADC_DATA is entered from IC201 to IC501.
 If no signal, check AVCC_3.3V & DVCC_3.3V (ADC) for IC301. If is NG, replace it with a new one.
4) Check the following I2S audio signal flow from IC501 to IC601. (Refer to Item 6-2.)
 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 6-1.
 If AMP is damaged, replace it with a new one.
6-6-3. Service hint (Any picture/ Remark)
< PORT. IN function signal fl ow >
ONE POINT REPAIR GUIDE
Pin15:DSPI_MCLK
Pin15:DSPI_MCLK
Pin16:DSPI_LRCK
Pin16:DSPI_LRCK
Pin17:DSPI_BCK
Pin17:DSPI_BCK
Pin29:PT_L
Pin29:PT_L
Pin30:PT_R
Pin30:PT_R