Go Video ddv9000 - no sound when copying
 

I just picked up a used Go Video DDV 9000 - a dual deck VCR. Everything
works great EXCEPT when I copy a tape from deck 1 to deck 2 there is no
sound on the new tape. When I watch the original tape on Decks 1 and 2
the audio is fine. Am I doing something wrong that I can adjust through
the menu? Or does this sound like a professional repair and, if so,
does anyone have an idea of the cost? Thank you.