How to measure available current of the power transformer?

[engels]

I'm afraid you've already seen my numerous posts here and there. I'm having fun with an old destroyed ~1953 Douglas radio which I want to transform into a rocketship. The original circuit used one 7C5 (6V6-loctal) output tube plus a couple of radio tubes and AZ21 rectifier.

After an extensive investigation I came to conclusion the power transformer was not designed for this radio properly: 5V filament is wired to the rectifier via a 10ohm spring resistor (AZ21 works on 4V filament), the 360V output windings of the transformer go straight to the rectifier which should accept not more than 300V, rectified 360V (400+) should be way too much for a single 7C5 in a radio (it's not even a champ) etc. etc.

The radio was completely broken and did not work, so I could not measure currents and voltages in the circuit. It does produces about 375-0-375V + 6.3V +5V, that's what I'm able to measure with everything unconnected. The power transformer looks an overkill for this radio, so I wonder what the transformer is capable of (maybe at least a PushPull 6V6 12-watter?). I'm not after recreating the original radio, I'm keeping only the chassis and the power transformer (even the output transformer is way too small and it is mounted on a 4" speaker's frame).

My question is:
How to measure how much current is available from the transformer?
Consider me a dumb newbie with only a couple of small amps built and repaired. I'm inexperienced and do not know anything about electronics.

[MooreCowbelle]

deleted