my buzz fix method
joerg at openmoko.org
Mon Apr 6 13:59:21 CEST 2009
Am So 5. April 2009 schrieb Rask Ingemann Lambertsen:
> On Fri, Mar 27, 2009 at 03:34:00AM +0100, Joerg Reisenweber wrote:
> > Regarding your low volume: did you check R4303? (It's the one below the
> > pads and right side to C4303, the one you borked and replaced. It's
> > mentioned in my SOP paper) R4303 is not mentioned in your story if I
> > miss anything. Usually it's 0R and it's amazing you get *any* signal at
> > from mic if you haven't replaced it by a ~2k2k (probably anything between
> > 400Ohms and 3k will do, though I learnt by your report even a 0R will do
> > least partially :D ).
> Joerg, could you clarify the significance of R4303 a bit? For example,
> how would I tell if it has 2.2 kOhms or 0 Ohms without measuring it (on a
> device without the buzz fix as well as with the buzz fix)?
Probing is the *only* way you can tell afaik.
We are basically grounding upper end of mic with a huge capacitor (AC), so we
need some R >>0Ohms on the lower end of mic to get some signal at all.
> The 100 uF capacitor is just the C4306 which isn't installed by default,
Without checking for correctness of #4306 basically yes.
> MICBIAS is also supplied to the headset mic (location 44xx). Would it do
> any good to add a 100 uF capacitor somewhere in that area too?
Nope, for a number of reasons it won't work, just break function of hs-mic
completely. See explanation some lines above. HS-Mic is singlen-ended (lower
pin connected to GND)
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