GSM-noise "buzz" issue
joerg at openmoko.org
Thu Oct 30 14:30:29 CET 2008
Am Mi 29. Oktober 2008 schrieb Angus Ainslie:
> On Wed, Oct 29, 2008 at 12:08 PM, Ole Kliemann <
> ole-om-lists-2008 at mail.plastictree.net> wrote:
> > 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?
> > 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.
> > Thanks!
> > Ole
> Hi Ole,
> I don't know whether Joerg has attempted the hardware fix yet.
Please see the whole thread to find we did quite a number of tests to verify
it, in TPE.
> I finished
> mine yesterday. Attaching the bead to the pad of pin 4 does NOT fix the GSM
> buzz issue.
Attaching the bead is *not* the fix exactly, cutting the connection from
JK4401:4 to coppertrace is considered the fix.
Anyway it seems you tried to achieve this by cutting the contact from JK4401
(your first picture). Alas it's not clear if you correctly isolated pin4-pad
on PCB, so to me it looks like you soldered the bead on the pin4-pad and
maybe you just shorted the tiny gap between PCB-pad and the metal-stub where
you cut off pin4-contact on JK4401, while soldering the bead.
Cutting the contact sure is a good thing, anyway I recommend to isolate pin4
PCB-pad by some plastic, so it is securely NC and in some distance to
JK4401:4 metal spring. (see:
Then do first test to find buzz is gone.
Then place bead to pad of R4404 NC, or even piggyback it to C4405, and connect
to upper golden contact of JK4401, above pin4. (Please note you need the bead
only for hs mic function, which may still be broken when using it during GSM
> There are a couple of pictures.
> Connector with pad 4 removed:
> It's a little hard to see, in this photo the bead is soldered standing up on
> pin4 with a jumper wire from the top of the bead to the side of the headset
> With this change the buzz is just as bad as ever.
> Angus Ainslie
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