I have a Pioneer sk-21. I am having a problem with the tape speed being way to slow. I adjusted the motor speed about 5 or 6 times and each time there was no change in the speed of tape. All belts appear to be in good shape and present. I bought another motor thinking the motor i had was bad. Installed new motor, same problem. What else controls the speed of the motor or speed in general if it isnt the motor? Any help very appreciated, thanks.