Philco 42-321 volume issue

[old_coot88]

If the resistance element in the vol control were open at the ground end, it would cause what you describe (or if the lug-to-ground connection were open).

'Ground' in this instance refers to the isolated or 'floating' common ground buss, standard in most all post-1940 series-string radios. Sets with power xfmrs continued to use chassis ground.