Dee, since nobody else has answered I will say that something that was covered in a serger class I just took at The Sewing Workshop is that sometimes tension is not the problem.
First of all, exactly what trouble are you having? thread breaking? fabric puckering? or ?
Second, if thread is breaking, are you using a good match of needle and thread sizes relative to each other?
Third, if puckering or other edge issues, can you adjust the width of the finger OR the distance of the lower blade? Each adjustment will do something different (the finger affects the width of the overlock chain and the lower blade --- well on a rolled hem...never mind!)
Fourth, double check that the thread really is IN the tension discs before you start sewing (w/ pressure foot down you should really feel the tension esp on the looper threads) and proof by starting a good chain before trying anything w/ fabric.