Hello, and welcome to JustAnswer.com!My name is Jesse, and I'm here to help.
Try plugging in and unplugging a pair of headphones several times.
That makes no difference. I push up volume button and comes right back to mute. If i totally restart it will work for a few minutes then goes back to mute.
Try resetting the PRAM, by holding the P+R+Option+Command keys together while restarting. Hold the keys for 1 full restart.
Does not hold lastt about 30 seconds then returns to mute
Okay, if you open System Preferences (located under the Apple menu in the upper left corner of your screen), and select the Sound pane, is the box for Mute at the bottom of the screen unchecked?
Cant uncheck it. The sound will stay for about 5 min then automatically goes off.
Okay, but that box is checked, that's good to know.
Let's try this:1. Open a new Finder window (click the smiley face icon on the far left side of the Dock).2. From the Go menu at the top of the screen, select Macintosh HD.3. In the Library folder, go to the Preferences->Audio folder, and move the com.apple.audio.SystemSettings.plist file to your Desktop.
Make sure that System Preferences is closed when you do this, then reopen it and see if it works.
Still the same no change
NO tried several times. It will work for about one minute then like clockwork it goes off
NO sound when it starts up. I can use keyboard volume F key and will work but still goes off in about a minute or so. Doesnt matter about app.
OSX 10.8.2 I just reloaded it today. No change. It is almost like it is on a timer.
Yes i have done that as well and still same.
Nothing is changed
No it is not checked