I just picked up a working Model Twenty-One in so/so shape - missing the power knob, plastic grille has shrunk causing it to peel off the masonite. However, it works - though I cannot tell if the tuner is bad - got some static on 91.7, other channels are clear. For the time being I'm going to print a new knob, and have to figure out a strategy to restore the grille.
So... I've sort of always wanted one of these radios but now I realized, I never listen to FM. Or AM for that matter. Are there any minimally destructive ways to add an Aux-in for a line in source? Ideally I'd route any wires without drilling into the case. I don't have a good impression of FM transmitters, but could always give one a try.
If the answer is 'no' or 'burn the heretic' then I'll set it aside until I have time to restore it fully (per this guide: https://antiqueradio.org/KLHModelTwentyOne21FMRadio.htm).
Thanks!
John