Update:
After some thinking, I found that.
1. It's not the bearings. They don't behave that way when crashed.
2. Not the brake. It's not possible for it to give that much resistance to movement.
3. It's not the resolver. I took off the outer part to check it. That can be done without damaging it.
So, I was left with the rotor itself. And the cost of repair meant the motor was scrap anyway, so I took it apart. And sure enough, the string wound around the rotor to keep the magnets were broken. One magnet had forced it to break. I don't know how that can happen. As far as I can determine the magnet is not loose, it seems it has "grown" like a piece of rusting iron.
I sent the seller some pictures, and he promptly agreed to refund a good amount of the money. The deal was for motor and drive, and the drive works. I's a beast to tune though!
So I feel I got out of it with a bearable loss, and a spare resolver that I can use on a motor I have with an encoder for which I have no interface data (Fanuc).  |