Sound - LG OM5541 Service Manual

4. NO SOUND
There is no sound output by DIGITAL AUDIO AMP DAMAGE, repair the set according
to the following guide.
(1) BY DIGITAL AUDIO AMP DAMAGE (IN ALL FUNCTIONS)
[ Solution ]
Please check and replace IC700 on MAIN board.
[ How to troubleshoot (Countermeasure) ]
1) Check PWM_FL± signals from IC601 to IC700 each input function.
If no signal, check if I2S audio signals are entered to IC601.
2) Check the following I2S signal flow. < I2S audio signal Interface >
- MCS_BCK: IC501_Pin E1 --> IC601_Pin23
- MCS_LRCK : IC501_Pin D1 --> IC601_Pin22 (44.1 kHz)
- MCS_DATA_OUT : IC501_Pin E2 --> IC601_Pin24
- MCS_MCLK : IC501_Pin D2 --> IC201_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 PVDD.
If PVDD is abnormal, check the SMPS.
4) Check +12 V for driving the gate of AMP IC.
a. All the powers are normal, but if +12 V is low, there is possible for AMP IC to be damaged.
b. Remove L702, L706 one by one.
When removed a inductance, if +12 V is recovered, the IC connected to it was damaged.
c. Replace the IC with a new one.
5) Check the impedance between IC700_OUT_A/OUT_D & GND.
a. If the impedance is 0 Ω, the IC must be damaged.
b. After removing the heat sink, replace it with a new one.
[ Service hint (Any picture / Remark) ]
DSP IC501
MLC3730
176PIN BGA
FL ±
TAS5631BPHD
12.288 MHz
PWM
TAS5548
< I2S signal fl ow >
ONE POINT REPAIR GUIDE
< Waveform of I2S audio
interface signals>
< Main Board Top view >
3-6
MCS_MCLK (16.93MHz)
MCS_BCK(1.4MHz)
MCS_DATA_OUT
MCS_LRCK(44.1KHz)
L706
L702