I’m having an Eee PC 1015PX laptop which served me for 5 years now and I love it. Last time I reallised that headphone jack is not working in debian jessie.
As my headphone jack is dual purpose (headphone/microphone), pushing all volumes up in playback screen of alsa, purging pulseaudio, installing backports kernel none worked. Instead of playback screen of alsamixer I went to CAPTURE screen of alsamixer and there I selected internal microphone instead of headphone microphone! This release headphone jack as an output and fixed the problem!
Hope it helps 😉