Quoted from crwjumper:
Does anyone know how to remove the lower Newton Ball on a premium/LE? It won't center or re-seat correctly and I'd like to polish and smooth the centering/resting plates. I tried to remove it last night but couldn't figure out how to separate the ball from the plates. I was able to remove the pointy post and the two nuts and two wood screws, but then couldn't figure out how to proceed to separate the ball (above the playfield) from the plates/spring assembly (below the playfield). Has anyone done this?
If you've already removed the pointy post the captive ball should just unscrew from the top. You have to hold the round aluminum spring seat still (on the bottom of the playfield between the spring and the bracket), and if you had any loctite on it from the factory it may be a little difficult.
I had a similar problem so here's a couple of other things to look for.
Push up on the ball assembly from the bottom (before you take it apart), the spring should compress and the aluminum ring should fully seat against the playfield. If it doesn't it's probably because the spring is binding in the hole. I found that my spring was slightly too large in diameter and would not compress up into the hole. My mummy captive ball was fine, the clairvoyant wouldn't compress. So I took them apart and measured, sure enough one was bigger. I had Stern send me a new spring and now it fits fine.
That fixed most of the sticking but it still gets stuck occasionally because there is a slight flat spot on the bottom of the captive ball where the post is pressed into it. This flat spot hangs on the edge of the playfield socket. My mummy ball dosen't have a flat spot, it is perfectly round with a post coming out of it, and it never hangs up. I haven't replaced the ball yet but I'm certain that's the problem.