I, too, have one of these problem children. When you find your answer, please share. I'll do the same. Thanks to everyone who responded with possible solutions.

Y'all are amazing! I'll be back tomorrow to try the newest suggestions.

First, an apology for not getting back on this sooner. Real Life(tm) reared its sometimes ugly head. :)

Tammi, your site was one of the first I found when researching the problem with the 301A. Great information and I have followed your suggestions. Here are several pictures of the bobbin case area. Hope you see something obvious and fixable. I added more shots than you asked about but since a picture shows more than I can describe thought it may help. And the part number on the bobbin case is 45750.
[ATTACH=CONFIG]468816[/ATTACH] [ATTACH=CONFIG]468817[/ATTACH] [ATTACH=CONFIG]468818[/ATTACH] [ATTACH=CONFIG]468820[/ATTACH]

Cogito, what a wonderful offer. I may have to take you up on it if the above pix don't show anything.

sjdal, I hope some of the information I'm getting here helps with your problem child, too. ;)

Is that bobbin case coated in dried oil? Does that come off with a little bit of rubbing alcohol on a Q tip or is that just the lighting? I would be cleaning that up and clean up the little spring, too before I did anything more. If rubbing alcohol doesn't work maybe naptha. Some times the dried up oil doesn't come off that easily. It also looks like the tension might be tight but if you pull that spring off it and clean it inside and out, then put it back on according to Tammi's instructions you should end up with a good bobbin case.

No, the goldish color is with the photo. It's nice and silvery chrome shiny. I've already soaked it in rubbing alcohol and scrubbed it with a toothbrush and dried it well before trying to use it again. I've looked under the spring with a 10X loupe and there doesn't seem to be any dirt. But I can take it apart anyway just in case.

If you take the spring off you will need to reset the tension. resetting the bobbin tension may go a long ways to fixing your problem. Tammi has some good info here:
http://www.archaicarcane.com/bobbin-...obbin-tension/
she explains it much better than I can. It is easy to do. It would be where I would start. I didn't mean to insult you - the pics just look kind of dried oil colored. I know some times a light coating of dried up oil will keep things from moving correctly. I would also wind a new thread on a new bobbin to make sure everything is in good order. Then I would put in a new needle. Make sure the needle in in the right direction. The flat side goes away from the machine - grooved side toward the machine. Then thread from right to left. Use a good spool of thread. I had fits one day when I used an old spool of thread and the thread caught on a rough place. Tammi also has good info on the upper tension on her same web page. Check that out as well. Keep posting and we will see what will work for you.

Oh, goodness, not insulted at all. I'm open to any suggestions and sorry if my reply led you to believe there was a problem. The Singer 128 I rehabbed was a beautiful gold color where things were supposed to be nice and shiny silver color. I think it was a combo of dried machine oil and nicotine. YUK!

I'll work with the leaf spring tomorrow and let you know what happens.

Did you ever take apart and rebuild the upper tension? It is very easy to do - Tammi has probably the best info on that. Here is some more info: http://www.sewusa.com/Sewing_Machine...Singer_301.htm
When I rebuild I pull the whole mess out and clean the inner pin - some times it can be a bit gooey and not want to function right. Dried up oil, lint, nicotine, some times fuel oil residue from the furnace... sticky hands, lunch Clean it all off and then adjust.

Yes, I have dis- and re-assembled the upper tension according to the user's manual. Looking at the SewUSA link, seems to be the same thing. And, even though the instructions say it's not necessary, I did remove the stud and clean that area. All in all the machine was in very clean condition which was one of the things I checked as well as possible before I bid on it. Actually had a screwdriver with me and took off the top and face plate to look there. Was almost expecting to get my wrist slapped by the auction house as we had never been there before LOL

K, just a quick one before I go to bed, then I'll think on it a little more:
1. Here's bobbin case dis-assembly, on a FW case, so it's identical. Bonus ;) http://www.archaicarcane.com/tear-it...e-maintenance/
2. I like Jamie Wallen's troubleshooting for bobbin cases and tension problems as well, it goes a step further than my blog does, and if you use the pin like he does, you might get away with not disassembling. It's for longarms, but works perfectly fine for domestics as well: http://www.youtube.com/watch?v=Q1mRhcquZTM
3. I have noticed that there are a lot of things not mentioned in upper tension rebuild instructions. Try these videos (mine) that I did last week. It's a 201, but the internals and operation should be identical. The first 2 videos cover some slightly different things (I expand more on some things than on others in each) which makes them both worth watching.
http://www.youtube.com/watch?v=guYToL6Gegs - ON Machine
http://www.youtube.com/watch?v=kzFXRdNE_1s - Off machine assembly
http://www.youtube.com/watch?v=WxtQO2XSB4s - Fast tension test (This is a visual of what I describe on my blog)
4. Try changing the bobbin you're using. Wind another one and make sure the bobbin case snaps into place. Something about that bobbin is bothering me, but I can't put my finger on it. Does it sit flush in the case when it's installed into the bobbin case?

After this, I will wait for your responses and think of where we need to go from here.