Trego made radios in the 1920's. You may have a battery radio using 201A tubes? If so check schematics for Stewart Warner 300 series radios by clicking "Resources" above. Most early radios will be similar.
These tubes require 5 volts on the filament. Usually 90 volts is for the plates. The detector will be powered off a 22 1/2 or 45 volt tap.
Your speaker may have a field coil? A field coil makes an electromagnet. Resistance of this field will give an idea of voltage needed?
Norm
:IN NEED OF SCHEMATICS FOR A TREGO 5 TUBE RADIO AND A UTAH
:SPEAKER(CATHEDRAL STYLE) THAT GOES WITH THE RADIO. IT APPEARS THE SPEAKER REQUIRES A BATTERY SUPPLY BUT I HAVE NO IDEA AS TO WHAT VOLTAGE. ANY HELP WOULD BE GREATLY APPRECIATED.