I'm not exactly sure what you mean by "..finished digital modeling knob...".  One common problem with the JTV-69 (and I cannot believe this hasn't been addressed yet) is that the model select knob does not quite push the control shaft in far enough to switch between magnetic and modeling modes.  Quick fix is to pull the knob off and drop a small bit of cardboard in the hole to shim it up and allow more travel when it's pressed back on.