A customer recently imported a vintage Presto 75A disk recording lathe from the USA, with a view to cutting records in Europe.
He quickly discovered, like many people before him, that it was spinning a bit slower than it should, when operated from 50 Hz mains, via a simple step-down transformer. As with most vintage record cutting machines, the platter is powered by a synchronous AC motor, which “locks” to the line frequency.
As with the vast majority of disk recording lathes of US manufacture, this 1956 Rek-O-Kut Model V was configured to spin at the correct speeds when powered by 50 Hz mains. One of our customers imported it from the USA and wanted to run it at 230 VAC/50 Hz European mains power. We have encountered this situation countless times by now. We recently also described how we converted a Presto MRC16 to 50 Hz operation by making new rubber rollers to different dimensions, while some years back, we developed the first version of Type 191, a stable electronic frequency converter for professional disk mastering lathes, which are often impractical or costly to convert by other means (Lyrec direct-drive motor on Neumann lathes, belt driven Scully lathes, gear-driven Fairchild systems, etc).