Function: The Philco 80 is a full-wave, directly heated, high-vacuum rectifier that rectifies AC voltage to produce the necessary DC voltage (often called B+ voltage) for the radio's other tubes.
Physical characteristics: It typically has a UX4 base with four pins, two plates, and two filament connections, according to VinylSavor. It can be found in a ribbed plate version, according to Etsy, or with an engraved base.
Applications: The 80 rectifier tube is suitable for preamplifiers or small power amplifiers that do not require high current output, notes VinylSavor.
Availability and Value: While the Philco 80 itself is not exceptionally rare, specific variations like those with "etched" or "engraved" bases might be of interest to collectors or restorers of vintage radios
Note: The term "etched" is sometimes used to describe tubes with engraved bases, referring to the markings on the base of the tube.