Linux – No sound out of headphone port on laptop

I cannot get sound out of the headphone port on a laptop. Headphones are plugged in, and sound comes out of the internal speakers. Windows behaves normally (sound switches to headphones when headphones are inserted).

It did work in Linux at one point, but something changed, we're just not sure what. Rebooting doesn't fix. This appears to occur whether or not PulseAudio is running.

Things I've tried:

• Rebooting. No effect.
• Booting into Windows. It works properly, so probably not a hardware issue.

• All of alsamixer. My only controls are this:

  • "Master" Volume bar & mutable, unmuted. Controls volume.
  • "PCM" Volume bar only. 100%.
  • "S/PDIF" Mutable only, currently muted, has no effect.
  • "S/PDIF" Default PCM", Mutable only, currently unmuted, has no effect.

• Killing PulseAudio. No effect. (It also won't stay dead! Something appears to be restarting it, and I can't tell what, but it is very annoying.)

• alsactl init 0, no effect.
• sudo rm -f /var/lib/alsa/asound.state, no effect.

General system info:

Ubuntu 10.04 LTS
Toshiba Satellite T135D-S1324

lspci says I have:

00:14.2 Audio device: ATI Technologies Inc SBx00 Azalia (Intel HDA)
01:05.1 Audio device: ATI Technologies Inc RS780 Azalia controller

Some edits: Yes, the headphones are in all the way.

This works in Windows: You plug headphones in, the internal speakers stop making noise, and noise comes out the head phones. Windows says I only have two sound cards: the HDMI port (which I don't care about) and the "sound card", which it claims is a "Conexant Pebble High Definition SmartAudio" In Windows, both the internal speakers and the headphone jack show up as one soundcard, which in my experience, is typical. (This is a laptop)