[R-390] R-390A 6C4 Mixers

[Jacques Fortin]

The 6C4 is one of the first miniature tubes issued.
The "double" 6C4 is a 12AU7.
The 6100 is the Industrial number for a 6C4, which bears the 6189 number in the double version.
Both the 6C4 and the 6100 have 6.3V, 150mA filaments.
The 6135 is a "ruggedized" version of the 6C4: 6.3V, 175mA filament, the double version being a 5814.
If the "A" suffix is added to any of those tube numbers, it means that the heater warm-up time is controlled for use in series strings of filaments.
The W suffix indicates a military spec. version, like the 6C4WA.

However, stay away of the "dwarf" sized 6C4W branded Raytheon, because it is not a "real" 6C4 and does not behave well as a frequency mixer compared to the standard 6C4 variants.

73, Jacques, VE2JFE in Montreal