[Arran]

It sounds like this is one of those odd sets that has the speaker coil/filter choke in the B- circuit rather then on the B+ side, so the filter capacitors may have a common positive rather then a common negative. Western Auto did not make their own radios, the chances are that this set was made by Detrola, Sentinel, Wells Gardner, or one of the other outfits that specialized in making private label radios.
Regards
Arran