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Originally Posted by maxm
I had the same problem with the radio knob actually, I managed to pull the radio chassis off the knob from the inside, leaving the knob secured to the front panel, instead of taking off the knob before removing the chassis.
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Yeah, I agree that can be confusing if you aren't expecting it.
Actually, a lot of series-string radios from the 60's have captive knobs like that. I think it was a UL safety requirement starting in the early 1960's or so that any series-string tube radio (or TV) that had metal control shafts had to have the knobs mounted in such a manner that they couldn't be removed from the outside of the set. The idea being, of course, that this would prevent the possibility of electric shock if a knob were to be removed while the set was plugged in, and someone touched a "hot" control shaft.
Just as you discovered, though, on those sets, you remove the chassis (or-- more likely-- PC board) from the knobs rather than the other way around.
Rather than resort to "captive" mounting of the knobs, manufacturers often switched to using controls having plastic shafts instead of metal-- this also met the UL safety requirement. Some of the cheapie Japanese import makes didn't bother getting UL approval, so those sets often had removable knobs with metal shafts anyway.