No sound on HDTV through YPbPr?

I am trying to use my xbox component cables to get an HD picture, but the problem is when I do I get no sound at all. The tv I have is an 18.5 inch Coby TV: http://i242.photobucket.com/albums/ff94/dumboy234/IMG00053-20110119-1651.jpg (view of the ports on the back of the TV)

The cables I have plugged in are green, blue, and red on the bottom row and the white and red on the top row. I get perfect picture but no sound (on the YPbPr TV mode)! But if I were to connect the yellow wire and switch the TV mode (AV TV mode)I do get sound but the quality is kind of blurry.

And if I connect either the white or red cable into the slot that says audio in, I still get no sound. I had to push back the the prongs that surrounded the the middle piece so it could fit into that slot.

Anyone know why this happens?

 

you use this color scheme i think your problem is solove

 

Yes it works that way but the quality is not as good as if I were to use the YPbPr component cables.

 

What's the green connector marked 'audio in'

 

I'm not sure what suppose to go in there. I had to push back the prongs that surround the white and red av cables in order to get them to fit in there, and still no sound.

 

Could it be for a stereo mini-plug?

 

I don't know what that is.

 

doesnt the xbox have a hdmi cable its supported on newer models.