Presto 75A Restoration Project

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.

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Presto 75A: 50 Hz 33 1/3 and 45 rpm Conversion

It would appear that 50 Hz conversions of vintage “made in USA” disk recording lathes are becoming rather fashionable! Last week we examined how we converted a Rek-O-Kut Model V by machining a new capstan and making a special transformer, Type 1760.

We have done 50 Hz conversions (and even some 60 Hz ones!) on many different lathes and turntables, using all of the possible methods of doing so: New rubber rollers, new capstans, new belt pulleys and even electronic frequency conversion (Agnew Analog Type 191 frequency converter) for professional disk mastering systems.

This week, we will have a look at the Presto 75A, a high quality machine, dating from the 1930’s, which was even used by the BBC as a broadcasting turntable!

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Presto MRC-16 Variable Pitch Modification

A rather optimistic gentleman arrived with a Presto MRC-16 disk recording lathe, inquiring about the possibility of repairing the broken suspension and making a cutter head bracket from scratch. He then asked about the possibility of figuring out some way in which lead-in, lead-out, and track mark spirals could be cut on this machine, which was originally intended as a very basic machine, with no provision for spirals, not even a hand crank. Then came the really ambitious part: He would ideally like to be able to adjust the pitch and if possible, control the lathe through his computer!

One glance at the steampunk aesthetic of the manufacturer’s name plate and the overall state of this primitive machine would have been enough to deter the average engineer, in fear that there might be something potentially radioactive hiding within…

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