Pulster fixe(s) and rework

Helge Hafting helge.hafting at hist.no
Wed Mar 4 12:15:28 CET 2009

Joerg Reisenweber wrote:
> Am So  11. Januar 2009 schrieb Alexandre Ghisoli:
>> Le Sun, 11 Jan 2009 19:07:40 +0100,
>> Konstantin <Chaosspawn23 at gmx.net> a écrit :
>>> Matthias Apitz schrieb:
>>>> Hello Christoph,
>>>> Could you please also make an offer for the hardware buzz fix in DE:
>>>> http://people.openmoko.org/joerg/GSM_EMI_noise/big-C_rework_SOP_rc2.pdf
>>>> Would be great!
>>>> Thx
>>>> 	matthias (one of your happy GTA02 customers)
>>> I second this one - offering the hardware fix for the freerunner
>>> would be great :)
>>> Regards,
>>> Konstantin (One of your other happy GTA02 customers ;) )
>> Yes, hardware fixes (rework) made by resellers would be great.
>> By fixes, I mean :
>> * GPS - SDIO fix (add a capacitor if I remember correctly)
> There's a sw-fix for that, which mostly "just works"
>> * Add a GSM IR resistor for deep sleep 
> Huh?
>> * Change the led transistor power hungry stuff
> Guys, this has been fixed for *ALL* FR ever sold!!!
>> * fix the GSM buzz
> ok, agree here.

If I ship the phone somewhere to have a technician fix the buzz, I 
definitely want the "small capacitors on headset output" issue fixed too.

The capacitor, combined with the resistance of earphones, form a 
high-pass filter.

The cutoff frequency is 1/(2*pi*R*C), where R is headphone resistance 
and C is the size of the capacitor. The capacitor in the FR has been 
reported as 1 microfarad. My headset is about 40 ohm, which gives a 
cutoff frequency of about 4kHz.

At 4kHz the sound is halved, and drops by 6db per octave below that. 
Above, the sound is almost normal. Unfortunately, most of the sound we 
hear is below 4kHz.

A headset usually works down to about 20HZ. If I want the cutoff 
frequency there, a 200 microfarad capacitor is needed.

Is there a plan for such a fix as well?

Helge Hafting

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