I have 3 motors here that are all exhibiting the same problem.
- 1 I don't care about, so it will be the guinea pig for any suggestions that come up.
- 1 would be a shame to have not work, but not the end of the world
- the last one is the Bernina 730's that I would like to resurrect if possible
All motors have good brushes. All are relatively clean inside. All of them spin great with no load, some even faster than I expected. One howls when it does it, but the other 2 are quiet. Both of the Singers have been disassembled and lubed, etc. The Bernina is still in the machine at the moment.
All of them stop or slow down significantly (to the point where they can't or barely drive a well serviced sewing machine), with the belt correctly or even loosely fitted.
I googled a lot, but I really couldn't find much for "electric motor runs with no load, but slows to a crawl or stops with load" (no, that wasn't my exact search )
My gut says that it's likely the windings, but if there's any way I can bring these motors back to life, I'd like to hear about any theories....
The former Singer shop owners in town used to claim that there was a "solution" they could put in the motor to revive it. I've never been able to tell if that's bunk or not.