GSM-noise "buzz" issue

[MarcO'Chapeau]

On Thu, 30 Oct 2008 12:11:47 +0200, Joerg Reisenweber <joerg at openmoko.org>
wrote:
> Am Mi  29. Oktober 2008 schrieb Ole Kliemann:
>> Hi Joerg and others,
>> 
>> I haven't followed the whole thread as I only understand 1%. So just one
>> quick and dirty question:
>> 
>> I have the two years EU warranty and am going to send my FR to my
>> distributor anyway because GPS is not working with the internal antenna.
>> (Independant of SD card.)
>> 
>> So if I send it in, is there any fix that could be applied for the
>> buzz? Or is it worth to wait, say another week, because there will be
>> something then?
> 
> Seems you always could "upgrade" to the 'botch' fix found in A7 (It
> *should* 
> work, as our TPE engineers found it worth to implement in A7 ;-):
> 
> replace R4403: 0R -> 2k2
> add C4306: NC -> 100uF (probably you won't find a 100uF to fit in
anywhere,
> so 
> a 47uF might kinda suffice. C4306 pads aren't existent in A5/A6, but you
> can 
> use pads of NC R4304 which isn't mentioned in public schematics)
> 
> 
> 
> A _yet_unapproved_(!) variant is to use a LM336-2.5 in place of the huge 
> capacitor, and to 
> change R4305: 2k2-> 860R (to make LM336 operate on >400uA, when setting 
> MICBIAS to VDD*0.9)
> You also have to
> replace R4403: 0R -> 2k2
> In theory this rework should yield even better stabilization of MICBIAS 
> voltage, the path where ripple caused by GSM RF is introduced to audio
> path.
> See all but first 6 pics at
http://people.openmoko.org/joerg/buzzfix-lm336/
> (first 6 pics are a nasty approach to cut pin4 using some dremel-like
mill.
> 
> Those are not related to LM336 fix)
> 
> 
> 
>> 
>> And - if you allow me to be off-topic - is there any improvement fix for
>> the headphone jack? I mean this hipass-filtering issue making music
>> sound quite tinny.
> a) place some decent 100uF (or as high cap as feasible) parallel to C4110
> and 
> C4111. Make sure you don't create another contamination path for RF
> creeping 
> inside big can - maybe use a ferrite ring to block RF next hole where you

> route some wires from those big caps inside can to C4110/11.
> b) *short* C4110 / C4111, and insert the 100uF somewhere else in
audiopath,
> 
> b1)e.g. near R4405 / R4407 (you can even replace these R by 100uF 
> capacitors).
> You should remove R4117 and R4117 then, and instead place these 1k from 
> JK4401:pin2 and pin3 (! for JACK_INSERT function) to GND
> b2) or even place the 100uF outside FR in the housing of your hs-plug or 
> 2.5->3.5mm adapter
> 
> HTH
> cheers
> jOERG
>

Hi,

Given all the work that is being done on these issues, I do not doubt that
a solution will be eventually found. I'm pretty patient, and I can wait
till we get there.

There remains a question that still deserves a firm and clear answer
though. Will we be able to send our devices to the distributors or to some
customer care center to get those fixes applied ?

Do we have some form of warranty ?

Cheers,
-- Marc-Olivier Barre --
 --- MarcO'Chapeau ----
- www.marcochapeau.org -