Raytheon is best known as a major defense contractor, but the company’s roots go far deeper, starting as a major manufacturer of vacuum tubes in the early days of radio. Today, the company is mostly ...

An 8-pin base with center post, metal shell, and glass insulator. T-shaped envelope. Stamped: "35Z3". Philco stamp on envelope under masking tape. Donor’s card reads: “Half wave high vacuum rectifier ...

English engineer John Ambrose Fleming received a patent for the thermionic valve, better known as the vacuum tube, on November 16, 1904. The two-electrode vacuum-tube rectifier, which Fleming called ...

[Eric] has an Atwater Kent 55C AM radio from the early 1900’s. He’s been trying to restore the radio to proper working condition. His most recent pain has been with the rectifier tube. The tube is ...

A 4-pin brass base with ceramic insulator, two parallel elements mounted vertically, tipless S-shaped envelope. Printing on base mostly indistinct: "U ...

WHEN an alternating current arc is established in a vacuum tube between a mercury and an iron or graphite electrode, the current only passes during half the time, namely, when the mercury pool is the ...