[Antipodal]

Big thank yous to BrendaAnnD,Radioroslyn and Morzh for your helpful replies . I have checked out the U.K. Vintage Radio Repair Dropper Calculations site. It is a model of elegant and accessible  explanation  and very helpful.At this stage though , I will probably stick with the transformer(s) option.
At the moment I'm pleased to report that the 1939  Chrysler/Philco C-1608 is now working again.I replaced most of the capacitors and repaired the speaker  cone and the set has proved both sensitive and powerful.The push button station selector responded very well to contact cleaner and now works well.I had to fabricate a new shaft for the tuning condenser as this had broken off right where the shaft comes out of its cover tube.
Next up is the Packard / Philco P4535. I have yet to figure out how to repair the manual tuning shaft  assembly which is used when you want to tune to a station other than those selected by the push buttons.This shaft,1/8 inch in diameter is the one turned by the big chrome knob in the centre. The thread on this shaft has been identified as left hand 1/8 inch American buttress thread.The thread on the rod is sound but unfortunately the nut in which it turns is stripped and that nut is the one which pushes and pulls the ferrite slugs in the permeability tuner.So, yes, I can still run the radio using the push buttons but not do manual tuning.If anyone has a nut of that specification I'd love to hear from you.
But a big shout out to the Philco Phorum and all the members.It is a great place to air one's concerns about the radio being worked on and I'm always so pleased and delighted to get such rapid and helpful replies.Cheers everyone.