Yosemite 10.10.2 No sound after update

Question

     Hi,
installed Yosemite 10.10.2 two days ago. Ever since the only sound that is working is the start up sound over the internal speaker.
After start up NO sound works, external speaker, internal speaker or HDMI output for any application.
I have no idea what to do. can someone help me??
My hardware setup is:
Mac mini (Late 2012)
2.3 GHz Intel Core i7
16 GB 1600 MHz DDR3
Would be super grateful for your help!
/HenkeB

Answer 1

Download and reinstall OS X Yosemite 10.10.2 Combo Update if you upgraded an existing Yosemite system. Otherwise, do this:
Reinstalling OS X Without Erasing the Drive
Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Reinstalling OS X Without Erasing the Drive
Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.
When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the Macintosh HD entry from the the left side list.  Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit Disk Utility and return to the main menu.
Reinstall OS X: Select Reinstall OS X and click on the Continue button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.
Also see:
Reinstall OS X Without Erasing the Drive
Choose the version you have installed now:
OS X Yosemite- Reinstall OS X
     Note: You will need an active Internet connection. I suggest using Ethernet
                 if possible because it is three times faster than wireless.