Mic volume extremely soft after buzz fix with SHR unstable

[Al Johnson]

On Monday 22 February 2010, Jan Girlich wrote:
> Am Montag, den 22.02.2010, 13:03 +0000 schrieb Al Johnson:
> > IIRC the buzz fix reduces the sensitivity of the mic input slightly.
> 
> I'm afraid something might be gone wrong with my buzz fix. Had a look at
> it yesterday evening and noticed one of the soldering points is really
> weak. Maybe that could be a reason? Too little of a connection from the
> capacitor to the resistor?

It can be hard to tell whether the joint is electrically good just by looking 
at it, and solder connections on those components are tiny. You really need to 
use a meter to test it, and I expect this was done by whoever did the fix for 
you, so it probably isn't the problem. If you are competent to test this, or 
know someone who is, the schematics and fix SOP are both available:

http://people.openmoko.org/joerg/GSM_EMI_noise/big-C_rework_SOP_rc2.pdf
http://downloads.openmoko.org/developer/schematics/GTA02/

> > > After fiddling around with the settings for a long time I ended up with
> > > setting the controls in the gsmhandset.state file back to these values.
> > > The other values are untouched.
> > >
> > > * control.48:   3
> > > * control.63:   'Mic 2'
> > > * control.12:   7
> > > * control.5:    115
> >
> > Controls 48 and 12 are on maximum, while control 5 has 12 steps
> > remaining. You still have scope to make the mic a fair bit louder if you
> > need to. 3, 5 and 121 would give the same volume level with less chance
> > of distortion.
> 
> Tried it. Still so soft that you have to yell really loud at the phone
> and only hardly can hear anything on the other end. I'm usually testing
> with my stereo, turning it on and putting the phone on the speaker. But
> I have to turn my stereo to levels it's getting uncomfortably loud just
> to hear a faint noise over the phone.

So 3, 7, 127 is still too quiet? In that case something may be wrong. Check 
the buzz fix, and also that the hole in the case isn't blocked.

> Fresh out of ideas
> Jan
>