There is a notch in the main steel shaft that the platter bushing slides down on. First and obviously, remove the center spindle. Using a dental tool or jeweler's screwdriver, finesse the round retaining ring so that the body of the ring lies in the notch. Then insert a jeweler's screwdriver under the edge of the ring with the axis of the screwdriver pointing across the hole that the spindle fits into, and pull the screwdriver back so that it presses against the side of the hole across from the notch. That side becomes the fulcrum. Continue pressing, and the retaining ring will pop up and off.
Now that the ring is off, you can remove the platter. What you will probably find is that the idler per se is fine, but that the idler arm assembly is sticky or frozen. You will also find that the speed selector knob is sticky or frozen. DO NOT FORCE THE BUTTON. The speed selector, the idler arm assembly and a long metal lever going to the main on/off switch comprise a single, unified assembly.
When this gets sticky or frozen, the machine gets stuck on a certain speed, say 33 rpm, the idler arm assembly won't move over and let the idler contact the motor pulley, and (this is scarier) in many cases the motor never turns off, potentially causing permanent damage to the motor.
There you have it.
Fred Longworth
P.S. Should you need one, an unnamed audio repair shop in San Diego has good used Dual 1219 motors.
