Bose Wave I AWRCC1 - intermittent to no sound output - loud popping & crackle sounds

[proxneo]

Dear reader

I have been asked to check out a faulty Bose Wave system belonging to a relative. The faulty unit produces loud intermittent pops and crackles. Sometimes there is speaker audio output (FM/AM, CD etc.), most of the time there isn't. This behaviour degraded over time fairly quickly, to the current situation where no sound is put out at all. Gently messing and wiggling wires, connectors or heatsink has no effect in force-replicating the problem. I have little experience in audio repair when it comes to (main)board electronic component faults. Bose repair WAS about 140$ (most likely a mainboard replacement), but I was two weeks too late between checking and actually applying for a repair (they removed the repair service for this one).

The large troubleshooting guide includes lots of information and diagrams. Unfortunately, it discusses the mk1, mk2 and mk3 in one document and not much can be found on troubleshooting this particular issue or the mk1 in particular.

• Visual checks indicate no blown caps, there appear to be no speaker wire faults (speakers have been tested separately) and no faulty power cord.
• I suspected the TDA7376B at first, but after replacing it there was no improvement.
• The unit has been tested on signal throughput. A 1kHz frequency was set on the AUX IN, and measured with an oscilloscope. Unfortunately, the signal was no longer detectable before it reached the HCF4052 chips, but I don't know if that is supposed to happen or the test was performed wrong.
• Everything else seems to work. (CD player, FM/AM, responsiveness to remote commands).

What would be a good starting point for further analysis and ruling things out?

Video of problem:
https://www.youtube.com/watch?v=ycrVmJIeMPc

Thank you in advance.

Kind regards,
proxneo

[прямо]

I had encountered a similar issue, albeit with a different system. It was an active monitoring speaker. Upon turning it on, a constant random loud pop and crackling noises can be heard, but any audio signal that went in, didn't come out through the speaker driver. I traced the problem to a single resistor in front of the amplifier IC input that has gone up in resistance (to an infinite Mega ohm range)
I replaced it with a proper value resistor and solved the issue.

I realized that checking every components is a tedious job and maybe too much work, but there's no shortcut around it :/

BTW, what is a 1K ohm frequency? Never heard of this before. Did you mean a 1 KHz test tone?
HCF4052 is an analog switch multiplexer IC. Most likely for switching between the different input sources (CD, FM/AM, AUX)

And if the audio signal (test tone) disappear before reaching it, that's a good place to start checking.

Good luck.

[proxneo]

[...]
Good luck.

Yeah sorry, 1kHz. Tired when I wrote it and am dealing with a different repair where ground resistance value was needed. I'll correct it to avoid confusion.

Thanks for the information. I was expecting that kind of answer. Was just wondering if it was indicative of a known or common issue, like some products do have. For example, AFAIK, the CD player on these Wave products can be quite problematic.
But I guess your recommendation, based on your experience, is a starting point. Thanks.

[ADRdaniel]

I'm sorry my reply isn't structured well. I worked on and off on it all day, and its continuity fell apart, but the information here would have saved me hours of digging arround.

Check that your tda7376B dual bridge "car radio" audio amplifier ic isn't shorted or OL
it's the "Multiwatt 15 package" ic on the huge heatsink.


My PCB says: 283027-001 for the power radio and audio board

photo credit: https://www.condoraudio.com/

Datasheet:
https://www.alldatasheet.com/datashe.../TDA7376B.html
https://www.condoraudio.com/wp-conte...ion-Repair.pdf

next, check both HCF4052B standby voltages
data sheet ( https://www.alldatasheet.com/datasheet-pdf/download/102812/STMICROELECTRONICS/HCF4052B.html )
pin 7 VEE Supply Voltage
pin 8 VSS Negative Supply Voltage
pin 16 VDD Positive Supply Voltage

i'd remove and replace the 4x 0.47uf 50v smd polymer caps by the speaker connectors (j150 j151)

The boards' vias are wide open, so you should be able to push a pin through them to help follow the traces back to exactly where the expected voltage or signal is lost or changed.

Here's additional info I found:
https://www.eserviceinfo.com/index.p...ose+wave+radio

Detailed Bose wave music system awrcc1 2 & 7 repair guide:
I respectfully disagree with his stance on "Chinese" the smd polymer caps. Those are fairly reliable, but shotguning all the caps is a reliable way to squash the issue.
https://www.condoraudio.com/wp-conte...ion-Repair.pdf

There are lots of wave series schematics, repair documentation, service manual, and other crap. Still, I don't see anything specific to the modern AWRRC1 ( except what I linked above), the "wave music system."

It seems series 4 is the newest model, and series three seems to cover 1996-20xx. I can't find any info specifically on series four, but the board appears very similar,
the key difference is all the caps are SMD polys on the newer ones
EXAMPLE: This is a schematic for the processor board for a wave Radio; the "u5d1 LC78622E" disc servo controller IC is present on my board but not labeled ( P86M-94V-0 05 01008 ), but I have an LA6571 iC 5-channel driver rather than a LA9240M is an analog signal processing and servo control bipolar IC
, and all digital logic ICs are on a separate shielded PCB connected via ribbon FPC from all the power audio radio and other analog stuff

The main power transformer has gone from the center doughnut hole of the PCB on 90's models to above on the left side ( facing rear) on this unit I'm working on today.
The PSU design seems more modern overall, with two unheatsinked TO-220 NPN transistors, whereas, as I recall, the last wave radio I repaired had a single TO-220 heatsinked NPN.

-Daniel owner of Advanced device repair , LLC

I'll post a repair video about the one I'm working on YouTube.
If you need to pick my brain about a repair or want to send one of these in for me to repair :
http://www.adr.tech , my business phone number is listed publicly there.