Most of us might get stunned for a while, when our sound system malfunction all of a sudden. If you have some knowledge in electronics, and have test instruments, yourself can troubleshoot and rectify the problem. I’ve done it myself, when my LG sound system has gone dead. Here I publish the procedure I did follow to rectify that fault. It too about two more days for me, as I’m not well experienced in service work. Patience and concentration are the most for this work.
[Check the speaker and all connection related to it [including the speaker wire continuity and connections, and make sure all of it are OK, belfore doing anything]
NO SOUND
There is no sound output in the CD FUNCTION, repair the set according to the following guide.
IN THE CD FUNCTION
Solution
Please check and replace IC501, IC600 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check CD_BCK, CD_LRCK, & CD_DATA signals from IC407 to IC501.
If no signal, check if the RF & servo signals from MD is entered to IC407.
Refer to the “No operation of MD” guide.
2) Check the following I2S signal flow. < I2S audio signal Interface >
- MCS_BCK : IC501_pin4 --> IC600_pin23
- MCS_LRCK : IC501_pin5 --> IC600_pin22 (44.1 kHz)
- MCS_DATA_OUT : IC501_pin85 --> IC600_pin24
- MCS_MCLK : IC501_pin3 --> IC501_pin82
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”.
NO SOUND
There is no sound output in the USB FUNCTION, repair the set according to the following guide.
IN THE USB FUNCTION
Solution
Please check and replace IC501, IC504 on MAIN board & IC3U01 on USB board.
How to troubleshoot (Countermeasure)
1) Check +5VU to USB board.
If +5.6 VA to pin2 of IC352(LDO) doesn’t come out, check pin2, 3 of CN351.
If +5.6 VA is normal & +5VU of IC352 pin3 doesn’t come out, then replace IC352.
2) Check USB D± from main board to USB board.
a. Check USB_HUB_DN/DP signals to IC501(pin16, 18)
b. Check USB1/2_DN/DP signals from IC501 to CN502 (pin5, 6, 8 & 9)
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”.
[Check the speaker and all connection related to it [including the speaker wire continuity and connections, and make sure all of it are OK, belfore doing anything]
NO SOUND
There is no sound output in the CD FUNCTION, repair the set according to the following guide.
IN THE CD FUNCTION
Solution
Please check and replace IC501, IC600 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check CD_BCK, CD_LRCK, & CD_DATA signals from IC407 to IC501.
If no signal, check if the RF & servo signals from MD is entered to IC407.
Refer to the “No operation of MD” guide.
2) Check the following I2S signal flow. < I2S audio signal Interface >
- MCS_BCK : IC501_pin4 --> IC600_pin23
- MCS_LRCK : IC501_pin5 --> IC600_pin22 (44.1 kHz)
- MCS_DATA_OUT : IC501_pin85 --> IC600_pin24
- MCS_MCLK : IC501_pin3 --> IC501_pin82
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”.
NO SOUND
There is no sound output in the USB FUNCTION, repair the set according to the following guide.
IN THE USB FUNCTION
Solution
Please check and replace IC501, IC504 on MAIN board & IC3U01 on USB board.
How to troubleshoot (Countermeasure)
1) Check +5VU to USB board.
If +5.6 VA to pin2 of IC352(LDO) doesn’t come out, check pin2, 3 of CN351.
If +5.6 VA is normal & +5VU of IC352 pin3 doesn’t come out, then replace IC352.
2) Check USB D± from main board to USB board.
a. Check USB_HUB_DN/DP signals to IC501(pin16, 18)
b. Check USB1/2_DN/DP signals from IC501 to CN502 (pin5, 6, 8 & 9)
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”.
NO
SOUND
There is no sound output in the AUX FUNCTION, repair the set according to the following guide.
IN THE AUX FUNCTION
Solution
Please check and replace IC202 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check AUX_L/R signals to IC202 (Pin23, 24).
2) Check if MCS_BCLK, MCS_LRCLK, & MCS_MCLK are entered from IC501 to IC202.
3) Check if ADC/MIC_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 IC600. (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.
If AMP is damaged, replace it with a new one.
There is no sound output in the AUX FUNCTION, repair the set according to the following guide.
IN THE AUX FUNCTION
Solution
Please check and replace IC202 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check AUX_L/R signals to IC202 (Pin23, 24).
2) Check if MCS_BCLK, MCS_LRCLK, & MCS_MCLK are entered from IC501 to IC202.
3) Check if ADC/MIC_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 IC600. (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.
If AMP is damaged, replace it with a new one.
NO
SOUND
There is no sound output in the PORT. IN FUNCTION, repair the set according to the
following guide.
IN THE PORT. IN FUNCTION
Solution
Please check and replace IC202 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check PT_L/R signal from MIC/PTB board to MAIN board.
2) Check POT_L/R signals to IC202(Pin9, 10).
3) Check if ADC_BCK, ADC_LRCK, & DAC_MCLK are entered from IC501 to IC202.
4) 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.
5) Check the following I2S signal flow from IC501 to IC600. (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.
6) Check if the digital audio AMP block is okay. Refer to “Digital Audio AMP” guide.
If AMP is damaged, replace it with a new one.
There is no sound output in the PORT. IN FUNCTION, repair the set according to the
following guide.
IN THE PORT. IN FUNCTION
Solution
Please check and replace IC202 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check PT_L/R signal from MIC/PTB board to MAIN board.
2) Check POT_L/R signals to IC202(Pin9, 10).
3) Check if ADC_BCK, ADC_LRCK, & DAC_MCLK are entered from IC501 to IC202.
4) 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.
5) Check the following I2S signal flow from IC501 to IC600. (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.
6) Check if the digital audio AMP block is okay. Refer to “Digital Audio AMP” guide.
If AMP is damaged, replace it with a new one.
NO SOUND
There is no sound output in the TUNER FUNCTION, repair the set according to the following guide.
IN THE TUNER FUNCTION
Solution
Please check and replace IC202, TU101 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check if TUNER_LR is entered from Pin1 & 3 of TU101 to IC202(Pin23, 24).
If no signals, Check +3.3 V for Tuner power.
Check if the Tuner control signals (CLK, DAT, CE, RST, GPO2) are entered from IC101 to TU101.
If it doesn’t work, replace TUNER with a new one.
2) Check if MCS_BCK, MCS_LRCK, & MCS_MCLK are entered from IC501 to IC202.
3) Check if ADC/MIC_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 audio signal flow from IC501 to IC600. (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.
If AMP is damaged, replace it with a new one.
NO
SOUND
There is no sound output in the MIC IN FUNCTION, repair the set according to the following guide.
IN THE MIC IN FUNCTION
Solution
Please check and replace IC202 on Main Board or ICM101 on MIC board.
How to troubleshoot (Countermeasure)
1) Check MIC_SIG signal to Pin10 of CN200.
If no signal, Check the signal to Pin1 of CNM101 on the MIC board.
2) Check if MIC_SIG is entered from Pin1 of CNM101 to Pin3 of IC506 (MIC AMP).
3) Check if the amplified signal is entered from Pin4 of IC506.
If no signal output, check +12 V for IC506, replace IC506 with a new one if it has a problem.
4) Check if MCS_BCK, MCS_MLCK & MCS_LRCK is entered from IC501 to IC202.
If no signal, check +5 V & +3.3 V for IC508. If it is abnormal, change replace it a new one.
5) Check if the digital audio AMP block is okay. Refer to “Digital Audio AMP” guide.
If AMP is damaged, replace it with a new one.
There is no sound output in the MIC IN FUNCTION, repair the set according to the following guide.
IN THE MIC IN FUNCTION
Solution
Please check and replace IC202 on Main Board or ICM101 on MIC board.
How to troubleshoot (Countermeasure)
1) Check MIC_SIG signal to Pin10 of CN200.
If no signal, Check the signal to Pin1 of CNM101 on the MIC board.
2) Check if MIC_SIG is entered from Pin1 of CNM101 to Pin3 of IC506 (MIC AMP).
3) Check if the amplified signal is entered from Pin4 of IC506.
If no signal output, check +12 V for IC506, replace IC506 with a new one if it has a problem.
4) Check if MCS_BCK, MCS_MLCK & MCS_LRCK is entered from IC501 to IC202.
If no signal, check +5 V & +3.3 V for IC508. If it is abnormal, change replace it a new one.
5) Check if the digital audio AMP block is okay. Refer to “Digital Audio AMP” guide.
If AMP is damaged, replace it with a new one.
NO
SOUND
There is no sound output in the BLUETOOTH FUNCTION, repair the set according to
the following guide.
IN THE BLUETOOTH FUNCTION
Solution
Please check and replace IC501 on MAIN board and Bluetooth module on front panel.
How to troubleshoot (Countermeasure)
1) Check BT_RX, BT_TX signal to Pin5, 7 of CN504.
If no signal, check the signal to Pin5, 7 and Pin1(+3.3 V) of on the Bluetooth module and cable connection state.
If there are no signal out from module, replace new module.
2) Check if BT_RX/TX is entered from Pin5, 7 of CN504 to Pin169, 170 to IC501 (DSP).
3) Check if MIC_BCK, MIC_MLCK & MIC_O_DATA is entered from IC501 to IC600.
If no signal, check VCC12(+1.2 V) for IC501. If it is abnormal, change replace it a new one.
4) Check the following I2S signal flow from IC501 to IC600.
If there is any trouble, check the power for each IC. If the signals are abnormal, replace it a new one.
5) Check if the digital audio AMP block is okay. Refer to “Digital Audio AMP” guide.
If AMP is damaged, replace it with a new one.
There is no sound output in the BLUETOOTH FUNCTION, repair the set according to
the following guide.
IN THE BLUETOOTH FUNCTION
Solution
Please check and replace IC501 on MAIN board and Bluetooth module on front panel.
How to troubleshoot (Countermeasure)
1) Check BT_RX, BT_TX signal to Pin5, 7 of CN504.
If no signal, check the signal to Pin5, 7 and Pin1(+3.3 V) of on the Bluetooth module and cable connection state.
If there are no signal out from module, replace new module.
2) Check if BT_RX/TX is entered from Pin5, 7 of CN504 to Pin169, 170 to IC501 (DSP).
3) Check if MIC_BCK, MIC_MLCK & MIC_O_DATA is entered from IC501 to IC600.
If no signal, check VCC12(+1.2 V) for IC501. If it is abnormal, change replace it a new one.
4) Check the following I2S signal flow from IC501 to IC600.
If there is any trouble, check the power for each IC. If the signals are abnormal, replace it a new one.
5) Check if the digital audio AMP block is okay. Refer to “Digital Audio AMP” guide.
If AMP is damaged, replace it with a new one.
AUDIO OUTPUT IS SMALL OR NO AUDIO OUTPUT
Audio signal output is small or not. when you power on the Middle Power Mini System.
IC700 ~ IC705
Solution
Please check and replace IC700 ~ IC705 on MAIN board.
How to troubleshoot (Countermeasure)
1) Please check if this system is on bass blast mode.
C, RL and RR make sound only on bass blast mode.
2) Check the IC700 ~ IC705 on your eyes.
3) Check the audio signal output check (Pin13 of IC700 ~ IC705).
First, check the Audio Data input (Pin3 pin of IC700 ~ IC705).
4) If the audio signal output has no output, try to change IC which has no output.
5) Lastly, check Speaker Terminal (TM700).
