Currently Being ModeratedFeb 20, 2013 6:58 AM (in response to Frederikhs)
Hopefully one of these steps should solve the problem.
System Preference > Sound > Output > Internal Speakers
Make sure Mute is not enabled.
Remove the headphone.
If you see red light in the headphone port, plug the headphone
in and out of the port 5 or 6 times to flip the microswitch inside.
Sound output may be stuck in the digital mode.
Reset PRAM. http://support.apple.com/kb/PH4405
Reset SMC. http://support.apple.com/kb/HT3964
Choose the method for:
"Resetting SMC on portables with a battery you should not remove on your own".
Currently Being ModeratedFeb 21, 2013 4:29 AM (in response to dominic23)
I tried resetting both SMC and the PRAM. I also removed and inserted a headphone jack into the slot, but none of it works...
The one thing that have changed is that there isn't a red light in the headphone slot
Currently Being ModeratedFeb 21, 2013 4:53 AM (in response to Frederikhs)
1. Restart. Click the speaker icon in the menu bar.
2. Finder > Applications > Utilities > Audi MIDI Setup > Audio Devices
Make sure that nothing is selected under "Mute" on the right side pane.