Sensibly equivalent¶ to:
The 6SR7 (Service code VT-233) is a double diode triode sharing a common cathode. The 'S' indicates that it is a single ended valve ie no top cap. The ratings are the same as the older 6R7 - with a top cap.
This triple sectioned valve was designed for superhet AM receivers. The first diode acts as signal detector feeding the audio signal via a volume control into the triode AF amplifier before the signal passes to the audio output valve. The second diode produces a DC voltage that is directly proportional to the audio signal and this voltage is used to control the gain of IF and RF stages of the receiver.
Compared to the pin compatible 6SQ7 this valve would exhibit lower gain in the triode stage.
The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 50 mm tall.
References: Datasheet, 1040 & 1043. Type 6SR7 was first introduced in 1940.
Absolute Maximum Operating Conditions¶
Updated October 25, 2013. shape:thin.metal.tube construction:glass.disc type:double.diode.triode age:1940.1950 base:io heater:6.3v pins:8 pin:1.m pin:2.g1 pin:3.k pin:4.a(d2) pin:5.a(d1) pin:6.a pin:7.h pin:8.h