[R-390] (no subject)

[k2cby at aol.com]

In general, ceramic tube sockets were considered "top of the line." In addition to being used in high-voltage, high-power and high-heat locations (ie most transmitter final amplifiers), they were also used in oscillators for maximum stability because the capacitance between pins changed very little with temperature. My own 390A has none, and I have not seen any in the odd 390A modules I have picked up over the years.
"Second best" are mica-filled Bakelite. These are the medium-tan colored sockets used throughout the R-390A. They were standard for low-power RF use.
"Third best" are the injection molded black Bakelite sockets. Although these are below "standard" for the R-390 and R-390A, they are certainly suitable for any of the audio stages, the VR tube and the rectifiers. They are not recommended for RF.
Last of all are the flat "wafer sockets" made up of two layers of phenolic sheet material. These were pretty much confined to cheap, mass-produced consumer products, but the military did use this type of construction for vibrator sockets and battery connectors.
Miles Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, NY 11963
k2cby at aol.com