Comment 23 for bug 688423

@David
I solved the problem by installing HDAAnalizer.py following instructions in www.alsa-project.com and follow David Henningsson instructions in the thread I mentioned earlier:

go to node 0x14, and make sure connection 0x17 is selected

After selecting connection 0x17, the internal mic started to work.
Also, I have added options snd-hda-intel model=laptop in alsa-base.conf.

I hope this info helps you find a definite solution to the problem.
Let me know if I can be of help.