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B4

 
See also:
The Dawn of Broadcasting in the UK - BTH B4 Box - BTH B4 Advert - BTH Range Advert - Which Valve Shall I Buy?
    
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This BTH valve seems to be labelled B4 but the B4 has a 6 Volt filament, as this is a later product than the 1923-4 B4 it is possibly a replacement type.
The filament voltage is marked as 2.8 Volts, suggesting dry battery operation. The internal envelope silvering obscures the electrode assembly.
The balloon envelope diameter is 35 mm and, excluding the B4 base pins, is 85 mm tall.
References: Adverts, boxes & 1003. Type B4 was first introduced in 1923. See also 1923 adverts.

 

Pin Connections
B4
1
2
3
4
a
g1
f
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
μ
6.0
0.25
120
-4.5
-
6,000
1.1
6.5
Updated May 21, 2015.
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