# Bose audio - volume button not working?



## mcMike (May 19, 2006)

Hello,

I have -99 TT with Bose audio (think it's the concert-model?). There is the CD-changer in the backseat-box and C-cassette in the front.

The volume button stopped working. When I turn radio on the volume is quite loud and ANY touch to any direction of volume will mute it.

Any ideas? Is this known fault? 
Any other options than remove the radio and disassemble it and try to change the potentiometer inside? Anyone know the part-code for new pot?

Thanks


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## rballtt (Jul 17, 2006)

Yeah I had that on my old S3 and it got progressively worse (especially in the cold).

The only thing to do is get a new HU.


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## mcMike (May 19, 2006)

rballtt said:


> Yeah I had that on my old S3 and it got progressively worse (especially in the cold).
> 
> The only thing to do is get a new HU.


*HU?* HeadUnit? as a front plate? Or am I totally lost here? 
Also, from where should I look?

Thanks.

ps. Cold indeed. This happened when the very first snow and below zero temperaturs came.


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## NormStrm (Sep 6, 2003)

I found this info on the audiowners group, hope it helps or points you in the right direction.

Re: [audiowners] Audi Concert radio/cassette-VOLUME CONTROL?Standard Header|Hide PaneSteve Bailey <[email protected]>AddThursday, 26 October, 2006 7:29:15 AMTo:[email protected]

Found this on http://www.audittcca.com/discussions/auditt/00005846

It explains what I tried to explain last night more fully.

"Just found this, hope it explains your problem.
No luck finding the chip type yet.

dead simple as to why... the radio has a microprocessor (Chip) with an
eeprom to store the memory in. this eprom has temporary memory which is lost
when power is removed and can be written to LOADS of times, it also has
permanent memory which doesn't loose it's data but can only be written to
say 10,000 times. the software for the radio writes into permanent memory
every volume adjustment, so after a while it starts to loose the memory of
the volume setting and hence blasts it out or very quiet.**** you can get a
new microprocessor reprogrammed with a modified software which is readily
available, but specialists charge bout Â£70. ****
I've tried sourcing this microprocessor but is seems obsolete.
you'll notice it only does it when the unit is cold normally, this is
because as it heats up, the material in the eeprom memory is more easily
written to."

And here:

http://www.erta.ru/review/chorus-problem_eng.shtml

Problem of Some AUDI Chorus and AUDI Concert Autoradio Models,
or "Delayed-Action Mine" from Blaupunkt Company
Autoradios equipped with standard details usually have a considerable
reliability margin in comparison with "mass consumption" devices. So it
caused our interest when in 1999 several AUDI Concert autoradios from
Blaupunkt Company with the same defect (the volume control system became
disable) were brought to our workshop. The initial analysis of this problem
took us to an inauspicious conclusion. Only in one case the reason was a
loosen screw of the volume control knob. In all the other cases the reason
of the volume control disability was the failure of the internal
non-volatile memory (EEPROM) of the system main microcontroller. To solve
this problem we had to replace the chip by a different one. To our great
disappointment those autoradios had a MC68HC05 Motorola microcontroller
(main MCU) although it's universally recognized as a highly reliable one.
By the way, this microcontroller is actually the most expensive electronic
detail of the autoradio.
Having decided to find out the reasons of the internal non-volatile
microcontroller memory failure, we have comprehensively investigated the
circuit design and the microcontroller software. The results were quite
unexpected! The main and the only reason of the microcontroller failure was
its software error in the part where the non-volatile memory record was
realized. The program slowly killing the microcontroller was "kindly"
designed by Blaupunkt Company.
Let us consider this problem in details.
The internal non-volatile microcontroller memory (EEPROM) is meant for the
storage of different data, which determine the system functioning. The
memory data record is stored even if the voltage is completely off. Usually
stored in the non-volatile memory are the tuner frequencies and all the
control levels at the moment of turning off (to bring the device to the
same condition as it was before the off-moment, even if it was disconnected
from the car voltage). There can also be stored the beginning and the end
of the tone control interval and other relocation "hardware-dependent "
data. At the modern development stage of electronics the non-volatile
memory always has the limit of the recording cycles amount. The EEPROM
wears out (molecular changes take place) during the "write EEPROM cycle"
procedure and equals 10000 cycles for the MC68HC05 family of
microcontrollers as Motorola Company guarantees. The real possible amount
can be several times bigger but this resource is limited anyway.
The generally used design practice is to take into account the EEPROM
resource finiteness and to write current levels of volume, fader, balance
and tone at the device-off-moment into the internal non-volatile memory.
Instead of it the Blaupunkt designers decided to write the data into EEPROM
after each minimum step of control (each regulator step) but not after at
least the whole user control. So if there are for example 32 steps from the
volume minimum to its maximum, the microcontroller will accomplish 32
"write EEPROM cycles" during the changing from the volume minimum to
maximum. Let us suppose that an average user changes the volume level by 5
steps and the EEPROM resource is not 10000 but for example 50000 cycles. It
is easy to count that the microcontroller will "die" after 10000 times of
the volume changing (or after 2-3 years if we suppose the volume is changed
10 times a day). 
We have located this volume controlling and "slowly dying" EEPROM cell in
the 01A8h microcontroller internal address space. It is easy to make sure
of extra EEPROM cycle records, checking the output VPP1 voltage (EEPROM
charge pump) during for example the volume changing.
The 01A8h cell begins "to forget" the data when the volume control EEPROM
resource is exhausted. It becomes apparent as the autoradio turns on with
an absolutely casual volume level and the control process becomes
unpredictable. At first the volume level malfunctions can be seen at low
temperatures only and the operating becomes normal with the device heating.
But the EEPROM molecular destruction process occurs with each volume knob
turning, so in several weeks or months the problems will take place
independently of the device temperature. The further usage of the fault
system will cause the failure of cells nearby and the device can be
completely out of operation.
You can the Blaupunkt autoradio models with such software error see in the
following table:

Autoradios
Part number
AUDI Chorus
7 646 243 380 ***
AUDI Chorus
*** 4B0 035 152A
AUDI Chorus A8
7 647 243 380
AUDI Chorus M4
7 648 245 380 4B0 035 152B
AUDI Concert
7 646 248 380 4B0 035 186
AUDI Concert A8
7 647 248 380 ***
AUDI Concert M4
7 648 247 380 4B0 035 186C
AUDI Concert M4
7 646 248 380 4B0 035 186B
AUDI Concert TT

AUDI Concert NAV
7 647 247 380
The full model name is usually marked on the right autoradio side.
Of course this error could not be ignored and the AUDI Chorus model
production was just stopped when they became to fail on a mass scale. The
AUDI Concert models (mentioned above) were also taken out of production but
replaced with the AUDI ConcertPlus ones, which didn't have such a problem.
It is very easy to diagnose this defect. If you see the fault of all the
controls ("Volume", "Balance", "Fader", "Treble", "Bass"), it just means
that the control knob is out of order. If the problems take place with the
volume control only (all the other controls operate well), it indicates
that the EEPROM microcontroller has worn out and you have to replace the
chip. 
To liquidate the recurrence of this failure after the microcontroller
replacement we continued our investigation. We managed to unassemble the
internal program of the MC68HC05 microcontroller, which is used in these
autoradio models. All the operations with the 01A8h cell were located. Then
the program was changed, and as a result all these EEPROM cell operations
were successfully readdressed to the random-access memory (RAM), which
resource is unlimited. Now we buy the "clean" one-time-programmab le
microcontrollers and program them with the object code of the revised
program. After the assemblage of the reprogrammed microcontroller to the
autoradio the recurrence of volume control problems is absolutely out of
question! The improved program operation can be easily checked by the
microcontroller output VPP1 voltage during the volume level changing.
We didn't change the Balance, Fader, Treble and Bass controls. Because they
are not used very often and this EEPROM cells resource (as we estimate) is
several times bigger than the possible period of autoradio usage.
In conclusion. Be careful! We know about a lot of cases when some
dishonourable "specialists" fix the worn EEPROM chip by its heating. Heating
can prolong the term (may be for some weeks) but is not able to solve the
problem completely. The real fixing is only the microcontroller replacement
with the one, programmed with the improved software.

On 25/10/06 11:38 pm, "Steve Bailey" <[email protected] blueyonder. co.uk> wrote:

> The problem is a well known one. Ours does it, but stops when it is warmed
> up. 1999 A4.
> 
> The chip that controls the volume, bass, treble and balance can only cope
> with so many changes in its lifetime due to a coding fault in the EPROM (or
> something... ).
> 
> Once you have reached the limit of changes (say 10000), it goes wrong. That
> is why the know works fine for the bass, trebly and balance, because you
> rarely change them. The volume knob is changed regularly so you reach the
> "fatigue life" of the chip sooner.
> 
> This sound like a load of coobblers, but I found it on the internet
> somewhere.
> 
> There is a place in Bath that will replace the chip for about Â£80 or so.
> 
> Steve
> 
> On 25/10/06 7:03 pm, "[email protected] com" <[email protected] com> wrote:
> 
>> When I got my car it had the Audi Concert system and never displayed any
>> problem with the volume.
>> 
>> the problem for me was the fact that it sounds absolutely horrible so after
>> a short while I just put in the system I had in my old car.
>> 
>> Is it piossible that only certain revisions of the Audi concert system have
>> this problem?
>> 
>> Elliot
>> 
>> 
>> [Non-text portions of this message have been removed]
>> 
>>


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## The Gachet (Jul 23, 2006)

Had a similar problem, was quoted 120 GBP + VAT to fix at a repair shop or an exchange with Audi for 150 GBP all in so I obviously took the later !


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## rballtt (Jul 17, 2006)

Wouldn't it be quicker to source a new Head Unit rather than read all that?? Pretty comprehensive response mind! :wink:


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## NormStrm (Sep 6, 2003)

rballtt said:


> Wouldn't it be quicker to source a new Head Unit rather than read all that?? Pretty comprehensive response mind! :wink:


 :lol:


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## mcMike (May 19, 2006)

NormStrm said:


> I found this info on the audiowners group, hope it helps or points you in the right direction.


Thanks. This explains it. 
I tried to look for the chip only to found out it's â‚¬56 (~40Â£). 
I could access eprommer and change it myself but don't think I'm gonna try it out because of the price.

Bah! Gotta look for new player and email my feelings to Bose... :twisted:


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## nolive (Aug 5, 2004)

mcMike said:


> NormStrm said:
> 
> 
> > I found this info on the audiowners group, hope it helps or points you in the right direction.
> ...


You will find out that BOSE does NOT make the HU on the TT (they don't make any HU as far as I'm concerned), the maker is Blaupunkt.

I've replaced my HU with an Alpine one sometime ago but still have it so if you change your signature (I work for FORD :wink: ) and send me a pm, you may have a replacement for less money you've been quoted 

Olivier


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## mcMike (May 19, 2006)

nolive said:


> I've replaced my HU with an Alpine one sometime ago but still have it so if you change your signature (I work for FORD :wink: ) and send me a pm, you may have a replacement for less money you've been quoted
> Olivier


PM sent. Signature changed


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## Nickasaki (Nov 2, 2006)

If anybody is interested i have a Bose radio/cassette player that is in purfect working order along with the booklet and code, It's out of my 2001 TT Roadster, I would be willing to sell for the right price ????


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## nickhamer (Feb 8, 2007)

Nickasaki said:


> If anybody is interested i have a Bose radio/cassette player that is in purfect working order along with the booklet and code, It's out of my 2001 TT Roadster, I would be willing to sell for the right price ????


...I realise it's been a while since you posted this, but have you still got that stereo?

(I'm having the volume control issue...as well as a CD player isue I've not even started on yet!)


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## John-H (Jul 13, 2005)

> These units suffer with a common problem of uncontrolable volume. You sometimes turn the volume down and it goes up full, sometimes it goes down full, other times it does just exactly what it wants to do!
> 
> REPAIR:
> 
> ...


Also here: http://www.codecard.lt/electronics/moto ... d_314.html


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## raybear (Dec 15, 2011)

hey buddys iam new on here names ray i have same problem found my audi tt mk1 1999 with bose had broken wires at back of iso plug. i tryed to repair but most other connector broke off and now to short to join back up. could anyone help me with wiring up a aftermarket head unit without a iso adaptor? cheers


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## armydan (Dec 7, 2011)

I had this on the headunit in my a3 before, changed the potentiometer and it worked fine after. Only cost a few quid for the parts and is quite easy to do if your handy with a soldering iron.


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## Porgie95 (Dec 28, 2013)

Hi guys

I have now gathered that this volume thing is old news.... I bought my audi tt in 2010 (v plate) and just thought it was a faulty stereo. She's been off the road for 18 months and just put her back on the road. Safe to say stereo is OFF! Lol. My question is, when I first had her I took her I took her to halfords to get a new stereo and they said to just wire it would cost £50 so I could have a new sound system! Is this true?

Any advice would be much appreciated,

Many thanks


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## blz-8027 (Sep 22, 2013)

Porgie95 said:


> Hi guys
> 
> I have now gathered that this volume thing is old news.... I bought my audi tt in 2010 (v plate) and just thought it was a faulty stereo. She's been off the road for 18 months and just put her back on the road. Safe to say stereo is OFF! Lol. My question is, when I first had her I took her I took her to halfords to get a new stereo and they said to just wire it would cost £50 so I could have a new sound system! Is this true?
> 
> ...


There's various adapters around ,just need to work out the one needed for the stereo you would be fitting 
http://www.ebay.co.uk/itm/PC9-404-AUDI- ... 25721f0773


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