Bose soundtouch 30 woofer works tweeters do not

[spdy]

I have a Bose Soundtouch 30 series III model that is not producing any sound
but everything else appears to work.
When I disconnect the tweeters (twiddlers as called by Bose) the sound starts coming from the woofer.
The woofer and tweeters are powered by two different ic's but using the same 24 volt supply which goes to zero when the tweeters are connected but remains at 24, with the tweeter disconnected.
The ic for the tweeters is TPA3100D2. I wonder if I should change this ic or is there something on its circuit that I can check.
With best wishes.
spdy

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

https://cdn.badcaps-static.com/pdfs/...fc56812a68.pdf

Leave the Tweeter disconnected and then check the Voltage between GND and each pin of the Tweeter connector on the board to see if it has Voltage on it.
BTW, uploading good clear pictures will also help.

[petehall347]

Re: Bose soundtouch 30 woofer works tweeters do not

check tweeters for shorting

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

Thanks budm and petehall347, the tweeters are functioning when I did a sound test from another source. Also I added another speaker, one only on the each of the output connections and immediately the sound (from the woofer) stopped coming and the voltage in the power supply went to zero.
I have a feeling I have to replace the tweeter ic TPA3100D2. I will try to also do the voltage checks as suggested.
With best wishes.
spdy

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

Thanks budm and petehall347, the tweeters are functioning when I did a sound test from another source. Also I added another speaker, one only on the each of the output connections and immediately the sound (from the woofer) stopped coming and the voltage in the power supply went to zero.
I have a feeling I have to replace the tweeter ic TPA3100D2. I will try to also do the voltage checks as suggested.
With best wishes.
spdy

Are you saying you connect ADD another speaker in parallel with existing speaker? Some amplifier may not like heavy load than what it is designed for so which can damaged the amplifier by over loading its output.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

No, I added the speaker in place of the tweeters, not parallel to them. If I do not connect the tweeters, but the ic remains connected and only connect the woofer, it produces sound, tested for over 45 minutes.
If I connect the tweeter it works for a few seconds before the smps goes from 23.8 volts to zero.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

budm, I forgot to mention that the voltage is 9.3 on alternate pins (zero on the other pin) with the tweeters disconnected and woofer(which is connected to a different ic) connected and sound coming.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

I just discovered that that the schottky double diode UH840 in the secondary section is showing over 120 volts, while the output capacitor is showing 23.9 volts and the unit has been working for almost one hour on the woofer only, with the tweeters disconnected.

The UH840 output shows continuity with the positive of the output capacitor. I checked UH840 after disconnecting the Bose unit and it was not hot to touch.
Isn't this voltage too high and why is it not burning up the capacitor, which shows normal voltage?
Also is the tweeter ic TPA31002d consuming too much current which perhaps makes the
smps to shut down or is there some problem in the current protection section?

[momaka]

Re: Bose soundtouch 30 woofer works tweeters do not

Sound like the TPA31002d IC may indeed be bad. But before jumping to that conclusion, it is worth noting that the speakers are BTL-connected to the IC outputs. Thus, 9.3V to ground doesn't necessarily indicate a complete short-circuit on the output of the IC. But 9.3V isn't quite right either. Ideally, that voltage should be at half of the Vcc input voltage (i.e. half of 23.9V, or about 12V).

Before replacing the IC, first check the input differential caps connected to pins RINN, RINP, LINN, LINP. If they are ceramic caps, make sure they are not short-circuited or leaky (if resistance on these caps shows below 100 Ohms, definitely remove them from the circuit and check their resistance again). Likewise, if the caps are cheap electrolytic ones, that could be the problem too.

On that note, also check any other surround ceramic caps around the IC for short-circuit / low resistance (with the power off, of course). And with electrolytic caps, note what brand they are.

I just discovered that that the schottky double diode UH840 in the secondary section is showing over 120 volts, while the output capacitor is showing 23.9 volts and the unit has been working for almost one hour on the woofer only, with the tweeters disconnected.
...
Isn't this voltage too high and why is it not burning up the capacitor, which shows normal voltage?

If that's measurement is of the unrectified, unfiltered voltage going to that diode, I would say your meter is just getting tricked from the high-frequency square wave output of the PSU. Either that, or perhaps you're not using the correct grounding point.

But since the voltage on the capacitor is what it should be, I don't think there would be a problem, especially since the woofer amplifier seems to be working okay.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

Thanks, so far I have not been able to trace out the capacitors to pins RINN, RINP, LINN, LINP. I do see two sets of bank of four resistors of about 103 ohms each for both the TPA31002d ic and the woofer ic. These appear to go to the input output circuitboard.
The input to the resistors for the TPA31002d IC shows 1.8 volts for three inputs and 3.2volts on the fourth.
The woofer bank of resistors shows about 2.3 volts on each of the four.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

I have not been able to get a circuit diagram for this, but found a service manual, which can be downloaded here




and would be grateful, if anybody can locate the schematic.

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

OUTPUT pins of the BTL should show same DC reading otherwise you will have large offset Voltage of 9.3V as you report that other pin is SHOWN 0V.
All you have to do is to check the DC V of the woofer speaker pins that I already suggested for you to do so.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

Thanks the woofer shows 11.9 volts each on both pins, to the ground

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

Thanks the woofer shows 11.9 volts each on both pins, to the ground

That is correct so the main result is the there will be 0 Volt offset Voltage on the speaker coil which is how it should be.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

I still cannot understand why the tweeter voltage is about 9.3 on one pin of each and zero on other in both speakers (tweeter disconnected) unlike the woofer which shows about 11.9 on both pins (woofer disconnected). The pins with zero show about 520 ohms resistance to ground.

Also the voltage to the resistors to the tweeter ic input pins show
1.8 volts for three inputs and 3.2volts on the fourth.

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

Just replace the IC.

[R_J]

Re: Bose soundtouch 30 woofer works tweeters do not

On a regular amp with + & - supplies you would normaly measure zero volts at the speaker.
On this ic it uses a single +24 volt supply so at the speaker measured to ground would be half the +24 volt supply (+12 volts measured to ground)
Note one side of the speaker does not connect to ground like a normal split supply amp.
From LOUTN to LOUTP you should measure zero volts but measure each to ground will be +12. (woofer working side)
On the tweeter side you measure +9 and 0 which suggests the internal fets are likely bad on that side or the gate drivers are bad, either way the ic is bad.
If you measure the voltage across the woofer LOUTP & LOUTN it will be 0 volts, measure the voltage across where the tweeter connects and it will show 9 volts, so connecting a speaker will shut down the amp.

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

I hope that the tweeter voice coil is not damaged by that 9VDC.

[spdy]

Re: Bose soundtouch 30 woofer works tweeters do not

Thanks, most of the other amplifiers I have seen hardly show any voltage at the speakers
and very often one of the outputs is grounded
The tweeters are OK and have been checked from another sound source again.

[budm]

Re: Bose soundtouch 30 woofer works tweeters do not

The amplifiers you are working on are using BTL output configuration that is why none of the speaker connection is connected to GND, look at the spec sheet of the IC.