No sound from Camcorder

Hi, I have a Sony Hi8 Camcorder (CCD-TRV138 NTSC) Handycam. I have only used it about 5 times and out of nowhere when I would try to rewind to hear the sound and watch the video there was no sound coming from it anymore. I have checked the volume which is all the way up too.
As of right now, the only way to hear any sound is to use the cord that you plug into the camcorder to the T.V. and the sound is just fine.
So I just wanted to find out if there is a certain setting that I need to change or what other options I have?

Thank you so much for any help with this annying issue,lol.

Keisha Mejia