I did encounter problems with the overlocker motor and had to take it to an electrical mechanic. The engine had to be coiled anew but is now as good as new. My perfect sewing station suffered next setback when my dear Bernina Record 730 came to a halt as smoke escaped the engine.
The Bernina Record 730 sewing machine is pure steel and only the motor and the motor belt will eventually give in. This particular piece is irreplaceable to me since it came to me after a very dear relative passed away. Luckily I had just successfully taken the overlocker to an electrical mechanic and I knew who to call.
This motor had to be re-coiled as well and I heard from the mechanic that this motor took a lot of work. So much actually that he had consulted a former colleague if it would be worth it before he started the job. Fortunately he got confirmation that these sewing machines are totally worth it for the customer and I was willing to pay for all the work needed.
Now the sewing machine works effortlessly and I will try to take good care of the motor by yearly professional service. And oiling regularly all of the dozens of spots marked with red paint in the machinery.