[AOD260, Realtek ALC272X, Mic, Internal] No sound at all

Acer Aspire One D260-A. Sound output and control via pulseaudio is fine and has been with 11.04, 11.10 and now 12.04. However, sound input from the internal mic has been mostly broken.

The internal mic was detected and the sound recorder application worked perfectly with 12.04 BETA 2 booted from a usb stick. I expected it would be fine when I upgraded to the new release, but it isn't.

When I boot my system (upgraded from 11.10 to 12.04 official releases), the mic doesn't record anything except low level static. Alsamixer shows it is at 100% gain and not muted. Pulseaudio control doesn't show ANY input device. Not surprisingly the volume control slider is at zero and the mute checkbox is unchecked, but both are greyede-out.

Wierdly, when I boot the 12.04 desktop official release from a usb stick sound recorder actually records my voice, but very faintly even at full gain. Pulseaudio control STILL shows no input devices and the volume control is greyed, set to zero and not muted.

Unfortunately I didn't keep the beta 2 system, so I can't look for differences - did any of the latest packages in the beta get forgotten when the release was cut (I don't see how that would be possible, but I have to ask).

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: alsa-base 1.0.25+dfsg-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic i686
NonfreeKernelModules: wl
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC272X Analog [ALC272X Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC272X Analog [ALC272X Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: jane 1822 F.... pulseaudio
                      jane 2578 F.... alsamixer
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0x58200000 irq 44'
   Mixer name : 'Realtek ALC272X'
   Components : 'HDA:10ec0272,10250349,00100001'
   Controls : 17
   Simple ctrls : 9
CurrentDmesg:
 [ 22.134596] init: plymouth-stop pre-start process (1257) terminated with status 1
 [ 22.360095] Adding 3998716k swap on /dev/mapper/cryptswap1. Priority:-1 extents:1 across:3998716k
 [ 51.672107] eth1: no IPv6 routers present
Date: Tue May 8 16:40:09 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaRecordingTest: ALSA recording test through plughw:Intel failed
Symptom_Card: Built-in Audio - HDA Intel
Symptom_DevicesInUse:
 1822 2578/dev/snd/controlC0: jane F.... pulseaudio
                      jane F.... alsamixer
Symptom_Jack: Mic, Internal
Symptom_Type: No sound at all
Title: [AOD260, Realtek ALC272X, Mic, Internal] No sound at all
UpgradeStatus: Upgraded to precise on 2012-05-04 (4 days ago)
dmi.bios.date: 04/28/2010
dmi.bios.vendor: Acer
dmi.bios.version: V1.01
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: AOD260
dmi.board.vendor: Acer
dmi.board.version: V1.01
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: V1.01
dmi.modalias: dmi:bvnAcer:bvrV1.01:bd04/28/2010:svnAcer:pnAOD260:pvrV1.01:rvnAcer:rnAOD260:rvrV1.01:cvnAcer:ct10:cvrV1.01:
dmi.product.name: AOD260
dmi.product.version: V1.01
dmi.sys.vendor: Acer