Ok, got some free time and tried most of these ideas. No difference with cotton thread top and bottom. No difference using quilting cotton, flannel, or denim. Cleaned tension with cotton cloth and a drop of SMO, no difference. The tension seems to work - I can see the disks moving together and apart as I turn the knob (with presser foot up). I haven't taken the tension apart yet. Have tried changing bobbin tension - no difference until it was really loose, then stitches were really bad. There are no dots of top thread on the bottom at any setting. I cleaned the bobbin area until it shone and added some extra oil to the underneath of the machine. The needle is facing correctly and the bobbin is seated correctly. Whew!
That being said, I found two other problems. One, the needle plate looks as if it has had multiple needles hitting it on the front side. I used some steel brushes to smooth it out, and my needle is not hitting it. What I think is a very big problem is that the sewing path curves outward if you don't hold the fabric in place. In all the older machines I've used, the seam was usually straighter if I let go of the fabric and just let the machine do it's job. This is just like when you need to get your car aligned because if you let go of the wheel you drift off left or right. In about 6 inches length, the path veered over an inch sideways - a nice, big curve. Does anyone know what causes that? Seems as though that could very well cause tension problems as well.
You guys are so great! Thank you so much for helping me!!
Margaret