buzz fix

Petr Vanek vanous at
Wed Mar 4 11:15:10 CET 2009

On Wed, 4 Mar 2009 09:09:50 +0100
Joerg Reisenweber <joerg at> (JR) wrote:

>Am Di  27. Januar 2009 schrieb Paul Fertser:
>> Al Johnson <openmoko at> writes:
>> > On Monday 26 January 2009, Christoph Siegenthaler wrote:
>> >> are there any updates from resellers, FIC or any half-official
>> >> DIY-tutorials on the hardware problems, i.e. the buzzing?
>> >
>> > This appears to have benefited from feedback regarding capacitor
>> > types 
>> > the few people so far to have attempted the mod, 
>> The feedback is that: you can use any cap, including tantalum. :)
>> > but more feedback is requested. The lack of feedback from people
>> > trying it may be why it hasn't yet made it past release candidate
>> > stage.
>> No more feedback is really needed. Everyone who performed the rework
>> confirmed that it eliminates the buzz. No single negative report. And
>> i guess at least 10-20 people have already tried the rework. So, the
>> reason that no reseller is doing it yet is probably due to
>> communication/business issues rather than technical.
>I'm not in charge any more to push this fix, but to me it seems we
>really don't need to quantify "how much it improves" buzz-issue.
>The cause and ways to creep in of buzz are well understood by now by
>some guys at least (and NO it's NOT the mic catching RF near antenna,
>it's pin4 of hs-jack), the bigC-rework is evidently (based on empiric
>and EE basics) eliminating the ripple we see on MICBIAS, and a
>gsmhandset.state file correctly using differential input mode
>(control.63 value "Mic 2") won't break audio function from unfixed to
>buzzfixed FR. Also we don't need any sophisticated test procedure, as
>* all devices are prone to buzz issue, so we don't need to prove there
>is buzz before fix
>* the big-C rework will either kill the buzz or you find you did sth
>wrong and mic stops to work. So any engineer doing the actual fix
>doesn't need any sophisticated "fix succeeded" test more complicated
>than that involved in replacing a lightbulb. Test call -> works ->


i am planning to do this on two units possibly (80%) this friday, i have
one unit with and other without the buzz issue(*), both will undertake
the fix. 

* the units were not used on same operator and in the same locations so
  i will try them first under the same conditions side by side to see if
  i can make my other unit buzz even if it didn't before.

If this can be an opportunity for you to have me to test anything,
please let me know.


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