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VT121

Sensibly equivalent to:
955 CV1059 D7271
See also:
The Famous EF50 of WWII - A datasheet for the 956 - Acorn Antiques - CV1059 short entry - Acorn Valve Base
    
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The acorn valves were designed to have low capacitances and therefore work to higher frequencies than the normal valves. The 955 triode was introduced in 1934, and has a 6.3 Volt heater.
The force required to seat the horizontal pins into the spring clips of the base was quite enough to crack the envelope. Eventually a zero insertion force socket was developed.
The 955 was later re-issued on a B7G base as the 9002.
The original box is torn and battered but shows all the essential data. The Crown and AM of the Air Ministry, the VT121, RMA 955 Type designation and the old stores code of 110E/40. The box is 35 mm square and 56 mm long.
The small envelope with even smaller triode within.
The evacuation pip on the right and within the heater connections and on the left the black of the getter.
The acorn envelope is 14 mm in diameter and, including the base pins, is 32 mm tall.
References: Private Communication & datasheet.

 

Pin Connections
1
2
3
4
5
f
a
g1
f
k

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
μ
6.3
0.15
250
-7
-
11,400
2.2
25
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated April 19, 2019.
shape:acorn construction:all.glass type:triode age:1930.1940 base: heater:6.3v pins:5 pin:1.f pin:2.a pin:3.g1 pin:4.f pin:5.k
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