[Arran]

That is one interesting property of those late 20s RCA sets, along with their Brunswick and Bosch look alikes, the power supply is mounted on a separate chassis that is connected via a screw terminal board. So it's no surprise that your friend was able to borrow a power supply from a working model 60 to use in this set to try it.
If you have the original power supply the power transformer, chokes, and filter caps are all mounted in cans potted in tar. The one advantage to this is that you can hide the replacement power transformer inside the old can and have it still look original as long as it will fit. How easily you can find a replacement is another story, you will need a power transformer with a 2.5 volt winding for the seven #27s, a 5 volt winding for the #80, and another 5 volt winding for the #71A.
Regards
Arran