RE: Subject: Re: the Bose Towering Inferno--still simmering?

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

> > OTOH, since _I_ know about this hazard, if I had a '91 200 w. Bose,
> > I would fix it.  Actually, the fix appears to be on the table as we
speak;
> > replace all the electrolytic caps on the rear speaker amplifier boards.
> > While I was in there, I'd throw in a fuse. Meanwhile, the bro has
> > simply pulled the plugs on his until he decides what to do about it.
> > 
> > DeWitt Harrison
> 
> Well, I'd like to have the bose engineer confirm that this 
> will fix the problem; 
<SNIP>

... I think you've hit the nail on the head Chris ...

Replacing electrolytic capacitors and adding fuses sounds like a quick fix
... but how do you know where a fuse should be added?  What about if the
problem is really that the polarity of the capacitor is reversed ... so you
replace the capacitor with one that is just as likely to fail?  The other
concern that I'd have is damaging the unit while attempting repair.  I'm
sure that there are a whole bunch of electrolytic caps inside that box, and
I doubt that Bose used the same quality PC boards and materials as you would
find in your home computer.  There is a real possibility that you will
damage traces while you're working to fix your problem.  I wonder if Audi
would take back a hacked up speaker module as a core?  

Perhaps the best thing that we could use in an ad hoc repair investigation
is a unit that failed.  This would provide at least some clues as to the
source of the problem.  

In my mind the best thing that we can do is to organize a directed
investigation to Bose (and/or AoA).  If someone has a contact at Bose I will
certainly write up my concerns and mail them to both Audi and Bose.  In my
earlier post I posed a number of questions that I would like to see answered
(I'll repeat them below) ... if anyone has others we can certainly add them.
>From my point of view what would be best would be to find that contact
person that supplied the information that we have gotten to see what their
recommendation as to how we should proceed.  We may very well end up with a
DIY solution in the end ... but it will be one that we know will address the
problem as it is understood by Bose.  

One problem that I see is that this is being discussed on other lists.  I'm
not scrubsided to anything other than the qlist, V8 and BA lists.  Perhaps
we could use the currently dead "torsen" list to coordinate this effort?  

Steve Buchholz
San Jose, CA (USA)

==============================

Here's the stuff I posted before ... 

While the information that you gave is far and away better than anything I'd
heard to date, I still have a few questions.  It would be great if we could
have them answered by someone at Bose since Audi seems to be uninterested.  

1) Is there anything different about the Bose system installed in the Audi
V8Q as compared to the 200Q?  While it may be that I'm not plugged into the
proper data, it sure seems to me that the problem is much less severe on the
V8s.  I would expect that there would be as many or more V8s produced with
the Bose system as 200qs.  

2) Is there anything that we could use to identify hazardous units like a
date code or part number on the speaker housing?

3) Is this problem only likely to occur on the units mounted in the rear
deck, or can the door mounted speakers have the same problem?

4) When Bose rebuilds a speaker unit are these capacitors replaced as a
matter of course?  Does Bose take responsibility for having the units
rebuilt or does Audi do this themselves?  

5) Is there anything that an owner can do to minimize the chance of
capacitor failure causing a larger problem?  Could the rating on a fuse be
changed or fuses added to the wiring?