The 12X4 was designed as a low voltage drop full wave rectifier ideally suited to vibrator power supplies for car radios. Type 6X4 is identical except for the heater rating.
The Silvertone made equipment and we can find no details of valve manufacture. The box around the Type identification is similar to RCA types.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 58 mm tall.
Absolute Maximum Operating Conditions¶
Updated December19, 2012. shape:thin.glass.tube construction:all.glass type:rectifier.fw age:1960.1975 base:b7g heater:12.6v pins:7 pin:1.a(2) pin:2.- pin:3.h pin:4.h pin:5.- pin:6.a(1) pin:7.k