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1638

Sensibly equivalent to:
VR54
    
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The RCA 1638 is a double diode for signal rectification or other low level duties. The glass envelope has been screened with an external copper metalisation that has then be painted bright red.
The 1638 was not an RCA Type code but a production code for the UK VR54 specification that also appears on the envelope. Jim Cross writes: 1638 is an American RCA type number for the VR54. During WWII, RCA made types 1637, 1638, and 1639 as replacements for Mullard types EL32, EB34, and EBC33, respectively.
The metalisation obscures the internal structure completely. Radiotron is an RCA trade name.
These valves were made for British service use and the envelope carries the RAF code VR54 as well.
The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins, is 59 mm tall.
References: Datasheet, 1040 & 1043. Type 1638 was first introduced in 1941.

 

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

 

Absolute Maximum Operating Conditions
Diode
Vh
Ah
Va
mAa
6.3
0.2
200
0.8
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated March 08, 2020.
shape:wide.glass.tube construction:pinch type:double.diode age:1940.1950 base:io heater:6.3v pins:8 pin:1.m pin:2.h pin:3.a(2) pin:4.k(2) pin:5.a(1) pin:6.- pin:7.h pin:8.k(1)
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