Two of my Sony units have these motors. The manual specifies that the speed can be adjusted from the back of the motor itself, not from a separate potentiometer. Unfortunately the hole in the back is "plugged" with some kind of rubber/glue. How are we supposed to adjust the speed of the motor. (My calibration tape generates a 3160 signal, wich is grossly out of spec.)
Assuming there's isn't a separate trimpot on a board (which I don't think is the case given the motor has 2 wires), you have to put a flat screwdriver through that hole and push it until you reach the trimpot inside. No worries as it will go through that rubber no problem, it's cut specifically for that.
