Sorry this took me so long to notice. If you apply 240 and the voltages are all 2x what you would expect, like 10v/12.6v/500+v you know it’s meant for 120v use. Don’t actually apply full voltage though. Just apply 10v or whatever and do the math to see the expected unloaded voltages.

I have been trying to find a good method to use that would indicate the current carrying capability of an unknown power transformer winding for months. Your method is the first ray of hope I have found. If you have any more information in regard to how to do this please let me know. Thanks in advance.

@@bobbysparky4299 Well its a simple method and quite accurate in my experience. As I said test it with a PT you know the specs of and you will see its very close. Should work with up to 250ma power transformers.

You need to take care doing it the way I do. I use the actual high voltage ac reading by connecting the unit into the outlet. take that high voltage reading from the center tap to either high voltage secondary legs. Disconnect the power and take the resistance reading of the wires you just measured the high voltage from. Then voltage divided by resistance x 25 = current . The late Gar Gilles of Garnet Amplification points out this trick in the Book he wrote called "The How and Why of Guitar Tube Amps as "Gar" Sees It"