Originally Posted by
lainealex
The Bernina tech guy said I should never adjust the bobbin tension myself, but that only a tech guy should do it at each annual service.
Did you ask him why? Is there some special tool that only techs have? Could you possibly mess something up by doing it yourself? Or do you have to pay a service fee every time you take it in to have the bobbin adjusted? If the answer to that question is yes, then I guess we know why he says a tech has to do it.
Personally I think it's hogwash. Check your manual to see if there are instructions on how to adjust your bobbin tension. I own several sewing machines; Brother, Pfaff, Janome, Singer, and I can adjust the bobbin tension on all of them.