One final question about the "play" in the 2150's volume control, as I am not 100% clear about it:

Does the volume control have play in its longitudinal axis? In other words, can one pull and push the volume control in and out a couple of millimeters from the face plate of the receiver? Or, when turning the volume control to the left or right, does the knob move a couple of millimeters before a change in volume is effected?

If the former is true, then I accept Outlaw's explanation for the phenomenon.