I would imagine that the difference is just the rectifier pack
(6 vs 4 diodes) and "whatever" ratio, and that if the DC main
supply got right, you might be in luck.
The DC main at 410V with only 2 of the 3 legs, might be
under "undervoltage lockout" for the control electronics.
If you can find a 240V-input Variac you might be able to
poke at that using your isolation xfmr (or maybe a better,
like 240:480V, for some extra oomph - Variacs I have, won't
go over 110% of line in) and substitute a proper rectifier set.
Might want to go chase service manuals on the web, see if
you can find any guidance about the proper DC rail voltage
inboard of the rectifiers & filtering.