Bernina 125 1953 - Technical Problem
 

Hello all,
The motor fails to turn the mechanism of the machine.
When I loosen the drive belts (rubbers) the engine immediately turns. When I reattach the straps, I see that it is trying but not succeeding. I checked the carbon brushes and they look fine, with sufficient length. I alcohol cleaned the commutator from soot.
On the other hand, I noticed that the motors in the same machines (https://www.youtube.com/watch?v=w0W7EBKvzIY) have what looks like a (paper brown) capacitor attached to the motor.
I don't have one.
There is of course a possibility that the old engine is already half dead and needs a new winding, but maybe one of you has another idea? Is this problem common?
Thanks a lot in advance - Michael

Are you able to turn the handwheel by hand, and make the needle go up and down? It might just be that the whole thing is frozen up?

Yes I am. The machine is free now, everything moves fine. Handwheel turning, mechanism is moving in all parameters.

Off the wall, but maybe... Could the belts have been replaced with ones that are too small for this machine?

Well I did install new belts, it was 2 or 3 years back and only now I got the time to get back to the machine and try to run her.
I hope that they are the correct ones.
They are 5mm red round rubbers (both, small & large) and were purchased relaying on the store's recommendation, that got all the relevant machine info from me.
I think it was from www.btrade.ch, though I can't remember for sure.