450
If you take it apart you might as well replace it because the chances are very poor that you will get it back together and not have it leak. You have to insert a broom stick, plunger handle, or something similar through the opening in the sink and catch it behind one of the two cutter bars. Then rotate the plate counterclockwise to free it. Then inspect inside the opening to see if you can determine what jammed it. If whatever did it is still inside, it will just jam again when you turn it on.