[jerryhawthorne]

Deckape, is the hum level changed at all by increasing the volume? If not, perhaps a little cathode to filament leak on one of the tubes in the audio output. The voice coil, a possibility if the wires were switched. If it has a hum bucking coil tied to the voice coil and things are turned around, it won't cut some of the induced hum from the field coil they have to be in opposition. Just my lame ideas. Congrats on getting this far!
Jerry