I believe that this is a hardware question but I could be wrong. So, I apologize if it isn't.

Essentially, my iMac G5 no longer recognizes my internal speaker. One day I plugged in my headphones into the headphone jack and when I unplugged them my internal speakers were no longer working. I went to system preferences and sound to see what was happening and it didn't even show an option for internal speakers. I was hoping to get some help in this area. So, any help will be appreciated. Thank you!