[BILL]

You need to find out what the resistance was of the original the original field coil was and use a resistor or a choke between the B+ ,then you need to find out if you still have audio out put transformer and if it's push pull or not, quite offen the out put transformer was mounted on the speaker.
Need obsolet batterys? build your own, I have several vintage portables , I've got another Portable Philco coming in now, one I have, Philco, has 1 1/2 volt "A" and 90volt "B", I use two "D's" in paralle. and 10 9 volts in series, I also have a Zenith Transoceanic Clipper 7G605[1942] I use 8 "D's" 6 in series two parallel= 9volts and then 10 9volts these radios will play over 50 hours on Dollar Store batterys!