I should have looked at it much sooner.
This area was the problem. The lower cog/arm thing for the belt tension was out of alignment, letting that cogged belt slip completely off. It (the tension wheel arm) was being stabilized by that lump of hot glue you see there, LOL. (This is the "after-fixing" picture, I forgot to take any "before"s)
[ATTACH=CONFIG]514387[/ATTACH]
It looks like some rubber pad behind the bracket has disintegrated. I found a manual online and it mentions a washer, but it was 4AM and I couldn't find one, but I did find a scrap of rubber foam pad and cut a couple rectangles out and put that behind the bracket, and now the belt lines up perfectly and stays put! I'm not sure that's really how it was originally, but it works.
[ATTACH=CONFIG]514388[/ATTACH]
I will have to find a washer but I couldn't tell from the scanned image of the manual where exactly it goes. I'm guessing between the screw head and the bracket arm?
This machine is such a tank. I took the top off and holy cow. This is the 332-260 so it has a built-in camstack. The belts on this thing are insane. I can personally verify that this machine is capable of sewing right into an 8 year old's finger, right through the nail, without hesitating. LOL
[ATTACH=CONFIG]514389[/ATTACH]
I plugged her in and she sews great! Amazingly quiet too. I'm so stoked!
Next up is a good cleaning and lubing, and some minor adjustments. And then a bigger house, so I can keep more machines set up at a time!!
[ATTACH=CONFIG]514395[/ATTACH]
I love how the bed folds down.
[ATTACH=CONFIG]514394[/ATTACH]
Getting at the dials with the lid on - this was a part I was NOT ALLOWED to touch as a girl:
[ATTACH=CONFIG]514400[/ATTACH]
Yaay! I just made my weekend, LOL.