That's exactly why I had asked if anyone knew of a way to get the knob loose because it DOES have the hex nut installed inverted with the outside of the nut facing into the wood of the cabinet and no way to remove it without damaging the cabinet which is still in pristine condition. one thing I noticed is that the panels on top of the radio for covering the record player are pieces of glass that are reverse painted to look like wood which I thought was weird and kind of unusual.
Also that empty "tube socket" is actually the power supply plug for the tuner section of the radio.
Also I was able to manhandle the record player out of the cabinet a little bit to get a view of the bottom side of the record player mechanism and sure enough it looks like it will be a nightmare to try and service it!
Also nobody answered my question about how to deal with the broken bass control pot.