Operating Manual for Dual Sew 3400?

I have a Dual Sew 3400, with no manual. On the front of the machine it says Pro Series Roary, Sew & Serge.
Having all sorts of problems with the tension, both top and bottom. It's really hard to take apart to clean...it's the most confusing machine I've ever had. Guess I should have stuck with Singer. Would appreciate any advice and better yet, how to get a manual
Thank You'
Kris