Looking at it, this is what I would assume the connections to be.
(Assuming between #1 and #2 is 100v winding and between #2 and #3 is 15v winding.)
I'd expect that the schematic shows 100V connection.
If you move the wires from the #2 termimals directly to their respective #3 terminals, you'll get 115V.
Connect line to right #1, then right #2 to left #1, and left #2 to neutral and you have 200V
Connect line to right #1, then right #3 to left #1, and left #2 to neutral and you have 220V
Connect line to right #1, then right #3 to left #1, and left #3 to neutral and you have 240V
Best to check on a variac to work out the ratios in each connection though.
Or you could just disconnect J6, stick a multimeter in and feed in a low voltage from another transformer with alligator clips for easy connection and a light globe for current limiting, say 12v or 24v, then multiply it out to find the correct combination.
Ie, for the correct combination for 120V in, at 12v input, you should get about 2.6V out, for 24V input, 5.2V or thereabouts.