I have a CMI [Chicago Model International] power unit for my HO trains. The voltage adjust potentiometer [train speed] has come loose and rotates. I can’t get a wrench under it to tighten it and I don’t know how to take the knob off. It doesn’t have a set screw and it won’t pull off. Can someone help tell me how to get it off? Also, who made these units and are parts available? Thx.
CMI seems to have gone out of business. Google turns up one of those units for sale, but no other information about the company or the product is available.