Audio doesn't work in OS X, but start up chime does.

[Firemarble]

I have a MacBook Pro (17-inch, Mid 2010 MacBookPro6,1 ) that the audio stopped working on.

The audio jack has a red light on in it. In Sys Pref, under Sound, in the Output tab, only Optical digital-out port is listed.

I have reset the PRAM and Reinstalled the OS. Why? Because when the mac is restarted, I can hear the start-up chime. So I know the audio does in fact work.

Anyone have any suggestions before I buy a replacement logic board off eBay and replace it?

I love having a 17-inch MBP and do not want to downgrade to a new 15.

 

[Intell]

Your Mac thinks that an optical audio cable has been inserted. You can try to fix that by plugging in some headphones a few times are varying speeds. Sometimes that will cause the Mac to register that there isn't an optical cable inserted.

 

[Firemarble]

Yeah I tried that too, for over an hour. No luck. :-(

Oddly enough, I just unplugged my headphones from the MBP, and while the audio still is NOT working, the red light is off.

 

[DeltaMac]

You hear the boot chime because that bypasses the headphone jack.
It doesn't matter if headphones might be plugged in - the boot chime sounds through the internal speakers by default.
You can't hear audio, because your Mac thinks that something is plugged in to the headphone port, switching out the internal speakers.
The red light is on inside the headphone jack, because the internal switch to change from analog (headphones/external speakers)to Optical/digital output is likely stuck. That red light is the receptor for the optical audio signal. You can try inserting, then removing headphones. A few times will often release that switch (the red light will be off then). Another possibility is to insert an optical adapter deep into that port (the optical link is deeper than the headphone jack, and you need what is called a toslink adapter.
http://store.apple.com/us/product/H...ink-optical-audio-cable-with-line-out-adapter
(Note the long extension accessory plug. That's the adapter you need to try.)
If you don't have access to that adapter (or don't want to purchase that for a test), then something that fits into the port can be useful. Just insert gently as far as you can push, then "wipe" it back out. In & out a few times, should reset that switch. If not, then could be something broken inside - not something you can repair.