Summary

The 27 was introduced in late 1927 as the UY227. It remained in production until World War II. In the early 1930s the various prefixes were dropped and it became plain 27. At about the same time the globe style bulb was replaced by the smaller shouldered type.
It was designed to be used as an amplifier or as either a grid-leak or biased detector. It has a 2.5 volt indirectly heated cathode.
Manufacturer: Hygrade-Sylvania Corp. Emporium, PA, USA

Physical Description

Shouldered glass bulb on 5 pin American (UY) base

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