Craig, You want to be _very_ careful if you attempt to run this
converter, especially in a Mills Violano. They produce more than
enough voltage and current to kill you.
They are also wired in a rather unexpected manner so you can get killed
in a variety of unexpected ways. Many parts of the Violano roll frame
and converter have lethal voltages exposed.
If that doesn't scare you enough, let me add that if you were to touch
the shiny part of the roll frame and one of the 4 terminals on the
converter at the same time, tune #1 would probably be the last one
you'd ever hear. In case you are interested, the little sparks that
you see while the roll plays peak at about 5000 volts.
One end of the converter is the DC [output to Load]. The end with
the terminals is the AC [input from Line]. BUT, they are probably
connected by a common wire somewhere in the system.
I do not know whether you are experienced in restoration or electrical
work, but if you do not know which end is which, I suspect that you
might want to reconsider any plan to repair or otherwise work with the
electrical part of the converter or machine until you learn a lot more
about it and have the help of an expert. Terry Haughawout and Dick
Hack come to mind. Not only could you see your Violano play the
"Firebird Suite" but it's possible that your family wouldn't have time
to properly restore the machine in time to play the "Funeral March".
Now that I think back on what I wrote, I have removed the answer to
your question. You really should contact Dick or Terry before you get
yourself into trouble.