In your case, since sound works elsewhere, this is more likely a bug in YaST’s test sound.
Try the following. … if you recall from above, I noted this list for options for the stac9200:
STAC9200
========
ref Reference board
dell-d21 Dell (unknown)
dell-d22 Dell (unknown)
dell-d23 Dell (unknown)
dell-m21 Dell Inspiron 630m, Dell Inspiron 640m
dell-m22 Dell Latitude D620, Dell Latitude D820
dell-m23 Dell XPS M1710, Dell Precision M90
dell-m24 Dell Latitude 120L
dell-m25 Dell Inspiron E1505n
dell-m26 Dell Inspiron 1501
dell-m27 Dell Inspiron E1705/9400
gateway-m4 Gateway laptops with EAPD control
gateway-m4-2 Gateway laptops with EAPD control
panasonic Panasonic CF-74
So I recommend you try each of the above items, one at a time, until you find one that works better for your PC. So lets start from the top of the list with “dell-d21”. So to try “dell-d21” change your /etc/modprobe.d/sound file (you will need root permissions to change it) to:
options snd-hda-intel model=dell-d21
options snd slots=snd-hda-intel
# u1Nb.dMH6nFzhrH7:82801G (ICH7 Family) High Definition Audio Controller
alias snd-card-0 snd-hda-intel
save the change and then as a regular user restart your alsa sound driver with su -c ‘rcalsasound restart’ and enter root password when asked for a password, then restart your mixer and test both sound and your mic. Pay special attention in case your mixer changes.
If “dell-d21” does not help, then try “dell-d22” and replace “dell-d21” with “dell-d22” in the /etc/modprobe.d/sound file, save the change, restart alsa, restart your mixer, and test. Do that for each item in the list.
Most will not work. Some may cause many error messages. Hopefully one will work.
If none work, we can try updating your alsa from 1.0.17/1.0.18 to 1.0.19, and I can provide you the 6 zypper commands needed to do that.