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W21

Sensibly equivalent to:
210VPT CV171 CV3804
    
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The W21 is a variable-mu amplifier pentode (possibly made as a beam-tetrode as it is from M-OV) with a 2 Volt filament. It was built in two versions, this with a B7 base cap and a B4 based W21 version, both were released in 1937.
The filament is for accumulator use and the anode is designed for dry battery operation with a maximum anode voltage of 150 Volts. The operating conditions shown are for the near equivalent.
The Marconi branding.
The external metal paint is connected to the base via a wire that is held to the glass by this adhesive ring.
The balloon envelope is 42 mm in diameter, and excluding the B4 base pins is 102 mm tall.
References: Data-sheet, 1040 & 1043. Type W21 was first introduced in 1937.

 

Pin Connections
B4
1
2
3
4
5
6
7
tc
m
g1
-
f,g3
f
-
g2
a

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
2.0
0.18
150
90
0
2.5
0.5
1.4
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated April 20, 2018.
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