There ARE still parts for your 7570 - amazing how rumors can get around!
Could be any number of things - from something as simple as a thread caught somewhere in the upper/lower tensions to the tension assembly to timing to any number of other things? You may have already tried some of these - hope this helps:
- Try "flossing" your upper tension - this is nothing more than running a heavyweight thread (such as upholstery or 12 weight thread) through the threading paths. Grasp the thread at the beginning of the threading path and the end coming through the needle and "FLOSS" (back and forth - just like you do your teeth). This will usually pull through anything that is gently stuck.
- Pretty much the same thing for the bobbin thread - if you're comfortable doing so, loosen the tension screw on the side of the bobbin case to make sure there aren't any little bits of thread fuzz stuck under the tension plate on the side of the bobbin case.
- Also remove the needle plate to allow you to better see the upper part of the bobbin system - if there are any bits of thread, etc. stuck in there, you may be able to see them and pull out with tweezers (turn machine off before you do this so the tweezers don't accidentally come into contact with anything).
If this doesn't work, you'll need to have a sewing machine tech look at it (I would recommend a Pfaff-trained tech as they're going to be the most familiar with your machine). The 2140/2144/2170 use most of the same parts - even the new CV still uses some of the same parts.