GSM-noise "buzz" issue

[Angus Ainslie]

On Thu, Oct 30, 2008 at 7:30 AM, Joerg Reisenweber <joerg at openmoko.org>wrote:

> Attaching the bead is *not* the fix exactly, cutting the connection from
> JK4401:4 to coppertrace is considered the fix.


 I cut the connection between pin 4 and its pad. The bead is now in series
between the pad and the spring that used to be JK4401:4.


> 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.
>

No there is no direct connection between pad 4 and the connector.


>
> 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:
>
> http://people.openmoko.org/joerg/GSM_EMI_noise/noise_stopped_by_cut_pin4/JK4401_isolate_pin4__2.jpg)
> Then do first test to find buzz is gone.


That's effectively what I did.  I attached teflon tape to the bottom of the
connector to isolate it. The buzz is still present.


> 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
> RF activity)
>

Right now I what to get rid of the buzz ( I'm going to attempt the A7 bodge
) and have the connector reattached so I can try and dump the GSM firmware.

Angus


-- 
Angus Ainslie
http://www.handheldshell.com/
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