iLoud Micro Monitor aka IMM, a PC Speaker came from IK Multimedia.
IMM is quite interesting for me because it used DSP as crossovers to Class D chips then output.
This loudspeaker came from my friend and failure symptom is no sound on right channel.
I used my cellphone to take pics during repair so the image quality is low.
IMM used a long tube as connection pipe after subwoofer to increase the base.
Interconnect cable covered by foam cotton, rest space fulfills absorbent cotton.
It used 4pins connector on daughter board of R-ch speaker, and quad-core cable to tweeter and woofer.
4 ohm 4-inch woofer, you can image that IMM may lack bass cause of small woofer and cabinet.
And the LED cable damaged by screw because of no fixed cable routing inside cabinet. Fortunately, no impact of sound quality.
Amp board connect to control board with pin header. Amp board changed PCB to V1.2 with more bead on R-ch than V1.1.
In the beginning that I think speak failure symptom may cause by Class D chip damage but give up this idea after tracing circuit.
Class D chip used TPA3130 and input buffer is JRC4560. Honestly, I don't like this OPA.
DC 20V input side, the main cap used 470uF 35V with unknow brand. It doesn't have room to change a bigger cap here.
Volume control used a one gang potentiometers B20K not regular 2gang. It may use MCU ADC to read the voltage on potentiometers and provide feedback to DSP as volume control. The crystal near VR add lots of soldering on it connected to GND.
There is some non-wetting joint on pin headers, but nothing helps after re-soldering. The big solder joint on left side using RCA socket GND pin to connect amp board and control board, which shows no AGND /DGND separations.
The DSP IC used ADAU1701, looks like a bit shift and some solder bridge on IC pins. After re-solder with heat gun then works temporary couple of minutes, but back to no sound after some pop noise. So, the main root cause may be DSP damaged.
The heat mapping shows both TPA3130 works normally in using thermal imaging camera, those two black items are series inductors on R-ch output path.
Those ICs looks OK unless DSP is a little bit higher and MCU is quiet low.
I forgot to take picture after repair, so I use older one to explain what I did.
1. Swap DSP IC
2. Re-soldering solder joints on RLC on DSP circuit.
3. Change the main capacitor (not necessary)
IMM is functional on both channel after swap DSP IC, but doesn't fix the no sound issue after 2~3mins.
I found some pin soldering joints are open, but the failure symptom is the same.
The no sound issue looks like clock abnormal during previously experience, but 12M x'tal is quite solid even the loading caps MLCC if not short to GND. I found some suspect solder joint crack after visual inspection and try to re-soldering all MLCC surround DSP than IMM back to alive.
My two suspicion on those issues.
1. The quality of SMT process is not good in the beginning, you may refer those SMD components during my photos.
2. Solder joint crack by sonic wave since this control board is inside the cabinet so all components are doing vibration test with sonic wave reflection.
Anyway, you may try to re-soldering if you face the same failure symptom.
IMM is quite interesting for me because it used DSP as crossovers to Class D chips then output.
This loudspeaker came from my friend and failure symptom is no sound on right channel.
I used my cellphone to take pics during repair so the image quality is low.
IMM used a long tube as connection pipe after subwoofer to increase the base.
Interconnect cable covered by foam cotton, rest space fulfills absorbent cotton.
It used 4pins connector on daughter board of R-ch speaker, and quad-core cable to tweeter and woofer.
4 ohm 4-inch woofer, you can image that IMM may lack bass cause of small woofer and cabinet.
And the LED cable damaged by screw because of no fixed cable routing inside cabinet. Fortunately, no impact of sound quality.
Amp board connect to control board with pin header. Amp board changed PCB to V1.2 with more bead on R-ch than V1.1.
In the beginning that I think speak failure symptom may cause by Class D chip damage but give up this idea after tracing circuit.
Class D chip used TPA3130 and input buffer is JRC4560. Honestly, I don't like this OPA.
DC 20V input side, the main cap used 470uF 35V with unknow brand. It doesn't have room to change a bigger cap here.
Volume control used a one gang potentiometers B20K not regular 2gang. It may use MCU ADC to read the voltage on potentiometers and provide feedback to DSP as volume control. The crystal near VR add lots of soldering on it connected to GND.
There is some non-wetting joint on pin headers, but nothing helps after re-soldering. The big solder joint on left side using RCA socket GND pin to connect amp board and control board, which shows no AGND /DGND separations.
The DSP IC used ADAU1701, looks like a bit shift and some solder bridge on IC pins. After re-solder with heat gun then works temporary couple of minutes, but back to no sound after some pop noise. So, the main root cause may be DSP damaged.
The heat mapping shows both TPA3130 works normally in using thermal imaging camera, those two black items are series inductors on R-ch output path.
Those ICs looks OK unless DSP is a little bit higher and MCU is quiet low.
I forgot to take picture after repair, so I use older one to explain what I did.
1. Swap DSP IC
2. Re-soldering solder joints on RLC on DSP circuit.
3. Change the main capacitor (not necessary)
IMM is functional on both channel after swap DSP IC, but doesn't fix the no sound issue after 2~3mins.
I found some pin soldering joints are open, but the failure symptom is the same.
The no sound issue looks like clock abnormal during previously experience, but 12M x'tal is quite solid even the loading caps MLCC if not short to GND. I found some suspect solder joint crack after visual inspection and try to re-soldering all MLCC surround DSP than IMM back to alive.
My two suspicion on those issues.
1. The quality of SMT process is not good in the beginning, you may refer those SMD components during my photos.
2. Solder joint crack by sonic wave since this control board is inside the cabinet so all components are doing vibration test with sonic wave reflection.
Anyway, you may try to re-soldering if you face the same failure symptom.
