From my measurements:
With 122VAC 60Hz line voltage:
HV secondary winding is 188VAC no load, and 186VAC, loaded with a FWB and 100 uF cap, feeding a 230V 40W light bulb (246VDC).
The transformer barely gets warm with this loading.
Calculating that the four 7591s consume about 200 mA total B+ current, and applying that a voltage doubler consumes about 3.6X the DC output current,
the 188 VAC winding is then good for at least 720 mA, probably closer to 800-900 mA. It's a beast
I have not yet tried it with a voltage doubler.
Filament is the usual 6.3VAC (7.2 VAC unloaded) for 4X 7591.
Third winding (brown-white-orange) is 55.2 VAC CT, unloaded, this is used for generating 24VDC for the four pairs of
series-connected 12AX7 filaments, and for generating the approx -26VDC for the 7591 grid bias.
http://oldtech.net/x202bS3.gif
http://oldtech.net/x202bS2.gif
http://oldtech.net/x202bS1.gif
HTH
/ed B