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Loftin-White

Meteor
(Silvertone model H)
Among the most rewarding projects of the 2014 Vintage Radio Service class was Tom Mathwig’s 1931 Meteor.  It was a five-tube set, branded by Sears, with a Loftin-White detector/output stage.  It used a type 24 detector directly coupled to a single type 45.  The same chassis was used in the Sterling model F.  The Sterling schematic was dated September 1930.  Some later models used a type 47 in the output stage.  I have never seen one in working condition ... until now.  Looking through volumes I, II, & III of the Riders Manual, we found more than 20 schematics using Loftin-White circuits, none of which were marketed by RCA, Philco, or Zenith.  In many regards, it was a brilliant design.  The voltage divider that provided self-bias to the type 45 also provided screen voltage, fixed bias, negative feedback, and stability to the type 24 detector/first audio stage.  The combination of direct-coupled audio, extremely careful RF construction, and a Jensen 8-inch speaker made this one of the best sounding “midget-radios” we’ve ever heard.
The drawbacks to the circuit are legion: a vulnerable 5,000-ohm speaker field, an 860-volt secondary on the power transformer, and no fuse in the voltage divider for the type 45 bias-supply made this a very risky design; if the type 24 went bad the Meteor could go up like a rocket.
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