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VT-233

Sensibly equivalent to:
6SR7
See also:
Metal Striptease
    
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The American Government specification VT-233 is a double diode triode sharing a common cathode and the commercial Type designation is 6SR7. 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: Data-sheet, 1040 & 1043. Type VT-233 was first introduced in 1940.

 

Pin Connections
IO
1
2
3
4
5
6
7
8
m
g1
k
a(d2)
a(d1)
a
h
h

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
6.3
0.3
250
-2
0.9
91K
1.1
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated October 03, 2019.
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
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