C-686

The Sparton type C-686 was one of the first tubes used for the Equasonne line. The type Sparton 486 was the replacement, at least since 1934. We can assume that the type 486 was designed in 1930 or later. Both were used for the Equasonne types 39 and 49, but even in saison 1929/30, the C-686 was used as original tube. See also Rider's volume 5, page Sparton 5-6. The tubes are not mentioned in "Röhren-Codex 1948", nor a 686. The Sparton 686 could be the C-686 without writing the "C". Arcturus also made the tube with the type number A-486. This tube has "daylight" blue glass.