So, you do not like the thought of a switch mode power supply in your precious field coil system? 

This field coil power supply uses the mighty Western Electric Mercury and Argon rectifiers to power your field coils.  They possess the cleanest operating characteristics of any rectifier I have used.  It uses geuine Western Electric rectifiers and choke input, of course....

For flexibility the supply has variable voltage and current.  Each is conveniently monitored on the front panel meters.  The unit was designed for lower voltage units such as the Western Electric 555, the RCA MI-1428, and the new Lowthers.   Additionally, custom units to power the higher voltage vintage RCA units MI-1443 and MI-1444 are available...

and I just had to show this photograph...

__________________________________________