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Bose soundtouch 30 no sound

S

spd

New Member
I have a bose soundtounch 30 whose sound has stopped, everything else works, wi fi bluetooth display. Even when I put it on AUX there is no sound. I can see the power board is supplying 23.5 volts to the ouput ic's
but I cannot get a signal tracer to get a signal on their input terminal. Does some one have a schematic?
I have the service manual but that does not have a circuit diagram or voltages.
Thanks.
spd
 
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Can you run some "self test" function?

Or, try to follow traces, sometimes I use the continuity "beep" in my DMM and just poke inside to find the next stage . Also, try to identify function selection ICs, those switches sometimes give trouble. Don't discard simply a bad capacitor blocking the signal.
 
Thanks, elnaldo. I have been trying to do this but with not much luck. I also thought I would put it on AUX and do signal tracing but not any success. I am not sure if this is a hardware or a software problem and without the circuit diagram
it is even more difficult.
I have seen a number of people have had this problem from the bose community site and they have mentioned bose repair would cost anywhere from 60 to 100% of the cost of a new set! From their service manual
it would appear they only replace circuit boards, that is why they have not put any schematics on it.
With best wishes.
spd
 
I think there must be some function selector and some volume and tone control at some IC.

Can you make a list of the larger ICs you see? Those with 24 pins or so.

We can check the datasheets and deduce the function. You can also trace the signal and check supply voltages to those ICS. I'm sure some signal is reaching one IC and not getting out of it.

Suspect any IC getting too hot.
 
Thanks elnaldo for your offer to guide me through this. The service manual of this available at https://elektrotanya.com/bose_soundtouch_30_series_i_ii.pdf/download.html and from there I was able to
see that there are two ic's for the output, TDF8599 for the subwoofer and TPA3100D2 which feeds the smaller speakers (called twiddlers by Bose).
I can see both of them getting a power supply of 23.5 volts but I do not get any growl from touching their inputs. From their datasheets it appears they can tolerate upto 24 volts. I only hope this is not too much and that is why they are shutting off. Also I do not get a signal on their input. I think they need a signal to switch on that they are not getting or they are going on mute.
There are no tone controls, but they probably get a voltage for gain (volume) control.
With best wishes.
spd
 
I'll check the service manual later.

I have to add, the only "Bose" I've fixed, with a weird problem, was "solved" or "fixed" lowering the voltage feeding one IC. The max for that IC was 10V, and it was working with more than 9.5. I lowered to 8V and problem was solved. So, in the meantime, follow the PCB traces to see if you have some resistor between the IC and the power supply, changing it with a larger resistor will lower the supply voltage to the IC.

Regarding your tests, you are measuring at the power amp modules. If they don't have signal at the input, the signal is lost before.

The "mute" pin must be at a low voltage. Datasheet specifies that.
 
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Hello again.

From the parts lists ICs, my suspects would be:

U28 Analog Switch (if it's related to audio signals, hard to tell without a schematic)
U502 Buffer
U503 Volume level

And not so common fails, but they can fail too:

U1105 ADC converter (Analog to digital converter)
U1101 DAC converter (Digital to analog converter)
** you can discard this ICs are working depending of the functions that work in the unit. I guess if you have some REC or AUX out in the unit, testing if you have sound there, you can deduce if the ADC or DAC work)

If you identify the ICs in the board, with a datasheet you can check the signal inputs and outputs
 
Once again many thanks for your suggestions and I will try to work on these. I also thought I would see if I can reduce the supply voltage, not sure if they there is a resistor in between as it appear the voltage on the large capacitor is the same as that on the output ic's, but still trying to check.
spd
 
By the way U503 and U505 are both HC40103M now I am not sure if the service manual is for this. Though this is Bose Soundtouch series 3, I doubt if there would be major change in the key components as the manual is for series 1 and 2.
Will check on the others and let you know for further guidance. Today I got a replacement flat ribbon cable that connects input output circuit to powerboard, as I thought I could read 5 volts on the i/o board
but not on the powerboard. but that did not make any difference.
spd
 
The powerboard mentioned in the service manual and i/o board both mention U503 and 505. I think the number is a misprint for powerboard and OK for i/o board.
 
I'd forget about the supply voltage by now. If those are the power amp output, they take the power directly from filter capacitors.

I'd trace a signal at the mentioned ICs .

Also, a dead ADC will have signal at the input but not at the output.

Check those U 503 505, check the pinout with a datasheet and check voltage and signal.

There will be a component where the signal gets in but doesn't come out. It could be a capacitor blocking the signal.
 
The voltages on U503 are as under
1 2 3 4 5 6 7 8
0 3.0 0 2.9 2.9 0 0 0


9 10 11 12 13 14 15 16
2.9 0 0 0 0 3.2 3.2 3.2


For U503

1 2 3 4 5 6 7 8
0 3.0 0 0 0 2.9 0 0



9 10 11 12 13 14 15 16
3.0 0 0 0 0 3.2 3.2 3.2


Both of these are HC40103M

Does this make any sense to you, I could not figure out from the data sheet?

Once again, many thanks and best wishes.
spd
 
I think those IC are not for audio signal. From the datasheets they are some kind of counter.

Try to identify analog switches in the signal path, or try to follow an audio signal. Start with a continuity test from the audio input to see the 1st amplifier stage. Or check the volume control IC to see if some signal is reaching it.
 
I am sorry it has taken some time but I have still not been able to fix it. I have been doing all sorts of tests on this. To recap, this has three main boards, the power board, the input output board,
which are below and a very small mainboard on the top. I was able to trace the audio up to the i/o board. The input output board has three flat cables one of which connects to the powerboard and the
other two to the mainboard on top.
Now I have been able to get the sound for about 2 seconds in the speaker, but the 24(actually about 23.5) volt supply goes to 0 volts on the power board. When I remove the flat cable connecting the two boards,
24 volt power supply remains and does not go to 0 on the power board. I found that the flat cable delivers this to a mosfet 4435d and a diode or transistor k3nd4 (could not find any data on this) on the i/o board.
I thought this is defective but I tried to give it 18 volts from an outside power supply to the mosfet (with flat ribbon cable disconnected from power board) but this voltage does not come down.
This is making me suspect the power supply in the power board is somehow defective. I have checked three big electrolytics, one which supplies 24 volts is 3300mfd 35v and two 470mfd 250v
which appear to be OK.
So any suggestions please?
With best wishes
spd
 
Further to my earlier message, today I discovered I am able to get the sound in the woofer (though not very loud), after removing the connection to the smaller speakers (Twiddlers). The voltage to the mosfet in the input output board does not drop to zero.
If I only connect the twiddlers and/or woofer, the sound comes for a couple of seconds only and the driving voltage, 24 drops to zero.
Both the twiddlers and woofer have separate IC's but getting 24 volt supply from same source. Wonder if the twiddler ic has gone bad or is there a power supply problem?
Any suggestions?
With best wishes.
spd
 
I'd say some short is dropping the power supply, not a defective power supply. You can test the power supply connecting a dropping resistor between the 24V and ground for a brief period. Try to draw 100 or 200mA (a 240ohm resistor will draw 100mA at 2.4 Watt, so use a large ceramic resistor or a couple of resistors in series-parallel to get 240 ohm and 5 watt, it will get hot quickly. A 120 ohm will draw 200mA and dissipate 4.8 Watt)

Can you cut the power to one of those output ICs? perhaps desoldering just the VCC pin, or cutting the PCB trace?

Are the speakers shorted? Can you try a dummy load instead of speakers?
 
Thanks, the first thing I checked was the speakers, they are OK and functioned from another audio source. I have a feeling I may have to replace the ic TPA3100d2 that powers the tweeters. I even tried using another speaker, on this ic one at a time and immediately on connecting the speaker, the sound stopped coming and the voltage dropped to zero.
I think the defect is is only around this ic.
With best wishes.
spd
 
I would look at the FAULT pin of the TPA3100, and the SHUTDOWNn and MUTE pins; Class D amps often have soft-start circuits, including a capacitor. And the capacitor can go s/c, thus never starting the amp. However, looking at the example design, the SHUTDOWN and MUTE seem to be logic-level, though, so maybe no soft start. Ah; check the behaviour of VBYP (see p24 of the data sheet); that serves the soft-start purpose.

Hopefully, you have the HTQFP package, not the QFN...

http://www.ti.com/lit/ds/symlink/tpa3100d2.pdf
 
cpt_paranoia,
Many thanks for your message, you are right this is an HTQFP package. I will try and look at capacitors etc around there. Have any of the members here seen a similar fault in an output ic, where the supply goes to zero
when speakers are connected?
With best wishes.
spd
 
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