Cat hair will jam up in the small gap between the gear and the bushing on the turbine and will cause enough friction to stop the turbine. I used a needle to dig out the hair and it solved the problem.
If you are only replacing the battery there is no need to remove the memory board. Cut the wires from the old battery as close to the battery as you can. Then cut the black wire from the new battery so that it is about 1/2 inch long. Strip the ends about 1/8 inch and solder. Slip a piece of 3/32 heat shrink tubing over the joint. Now cut the red wire so that it is about 1/2 inch long and strip as above, solder and cover with heat shrink tubing. It works!