buzz fix (was: Pulster offer - Freerunner now 249 eur)

Al Johnson openmoko at
Tue Jan 27 15:31:52 CET 2009

On Tuesday 27 January 2009, Helge Hafting wrote:
> Al Johnson wrote:
> > On Tuesday 13 January 2009, Yorick Moko wrote:
> >> buzz and gsm fixes are even documented on the wiki (no need to search
> >> in the e-mails)
> >> only the audio-fix (big capacitator to provide more bass isn't; hoping
> >> to see that one documented as well
> >
> > There's some fairly detailed discussion of audio mods on the hardware
> > list which could be copied into the wiki, but there is no 'official' mod.
> > I suspect there won't be one either, mostly because big caps won't fit in
> > the space available, and relocating them to outside the screening can
> > could easily reintroduce buzz.
> Another option:
> Short the too small capacitors, so there are no capacitors at all. Then
> add the big caps outside the screeming, but this time with no need to
> connect to anything inside the screening.  Just break the connection
> anywhere, and insert a nice big cap. The easiest place of all then, is
> obviously to add the caps to the headset. Of course then you only have
> one useable headset.

Yes, that's one of the options discussed, along with some resistors you might 
like to remove. You could put the caps in a 2.5mm to 3.5mm ( or even 1/4in) 
adaptor cable to make it usable with generic headphones. I don't personally 
like this solution for 2 reasons; one day I will forget and stick dc on a 
headset, and it will probably prevent use of the serial debug interface to 
the gsm. The second objection won't be a consideration for the vast majority 
of people though.

> Or break the connection between the plug and circuit board, and put the
> caps somewhere inside. There is lots of room above the SIM card.

This is harder than it sounds IIRC, but feel free to try. I had my eye on that 
space for caps too as the existing caps are very close to it. You could make 
a small hole in the screening can to pass the wires through, but would need 
to be careful to avoid creating an rf pathway.

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