MacBook Pro 2007 outputs sound to optical digital out by default

[misee]

Since a couple of days, my MacBook Pro (end of 2007, 15" 2.33GHz Core 2 Duo) does not output any sound to the internal speakers. Instead, it always outputs through the optical line out (at leas I think it does, since I can always see the red light).
I have tried manually switching output by going to the System Preferences -> Sound and then selecting the output tab. The only device shown is name: "Digital Out" type: "Optical digital-out port". Same when option-clicking the sound toolbar menu. When using headphones, everything works as expected, but when plugging them back out, it goes back to optical out.

I'm running Mac OS 10.7.1. The system had a clean install (formated the HD) just a few weeks ago.

Is there any way to "force" it to switch to the internal speakers?

 

[Detrius]

Sounds like a bad Left I/O board. Fortunately, they aren't horrifically expensive. It's just a pain to swap the board out.

 

[misee]

Thanks for the answer. But I'll be buying a new MBP some time soon, so I won't fix this (it's just one out of 3 issues I'm having). Got headphones, stereo plus an optical cable which my baby seems to have fallen for (they grow up so fast)

By the way, I just realized that I do get the startup chime. Shouldn't that also not work if it was a bad Left I/O board?

EDIT (October 2): I didn't do anything, but it suddenly started to work again.

 

[Detrius]

Not necessarily. I've seen plenty of machines that will chime but still have bad audio jacks.