Browsing on the net this week I found this article on machine tension on the Threads website with something completely new to me:
"Be sure your presser foot is down when you make the tension adjustment."
This is an eyeopener to me. I tried it and it really seems to work better than with the presser foot up. I never thought of this making a difference and sure have never heard about this. Did you know?
For more information on the subject see the original article.