LG CM4520 Service Manual page 30

5. NO SOUND
There is no sound output in the CD FUNCTION, repair the set according to the follow-
ing guide.
5-1. IN THE CD FUNCTION
5-1-1. Solution
Please check and replace IC601, IC801 on MAIN board.
5-1-2. How to troubleshoot (Countermeasure)
1) Check CD_BCLK, CD_LRCK, & CD_DOUTA signals from IC302 to IC801.
If no signal, check if the RF & servo signals from MD is entered to IC302.
Refer to the "No operation of MD" guide on Item 4.
2) Check the following I2S signal flow. < I2S audio signal Interface >
- DAC_BCK: IC801_Pin87 --> IC601_Pin4
- DAC_LRCK : IC801_Pin88 --> IC601_Pin5 (44.1 kHz)
- DAC_DATA : IC801_Pin83 --> IC601_Pin6, 9
- DAC_MCLK : IC801_Pin86 --> IC401_Pin44
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.
3) Check if "Digital audio AMP block" on Item 5-2 is normal.
5-1-3. Service hint (Any picture / Remark)
P/UP
DAC-BCK/LRCK/MCLK/DATA
< I2S Signal Flow >
ONE POINT REPAIR GUIDE
BU9543KV
RF+ SERVO DSP
MLC9800
MCS LOGIC
PWM
PS9854
3-11
< Waveform of I2S audio interface signals >