[Lucien Nunes]

I wonder whether the requirement for the specific mains transformer in the set for use with the vibrator follows from it outputting a non-standard frequency rather than a non-standard voltage. Perhaps the universal type has lower loss or more iron? Perhaps the vibrator unit has a tuned output filter that might reveal the frequency?

No hurry at all but it would be nice to see the circuit as I'm interested in early power supply arrangements generally. In the collection here there are both vibrator and rotary units for public address amplifiers. Cinema amplifiers were also sometimes equipped with rotary converters energising the amplifier's normal mains transformer from either DC mains or the 110V house DC, at 60Hz in the case of USA-made units.