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3A4

Sensibly equivalent to:
CV807 CV2390 DL93 E1485
    
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The 3A4 (DL93) is miniature output pentode is specified for both audio and transmitter use. For a small dry battery valve 1.2 Watts output in the HF range would be quite an achievement. The UK Government used these valves as the CV807 and both identifications appear on this exhibit.
The makers codes on the back. The twin filaments and their springs can be seen above the top mica and again exiting from the lower mica.
The tension springs and a glimpse of the wire grids.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 46 mm tall.
References: Data-sheet & 1040. Type 3A4 was first introduced in 1945.

 

Pin Connections
B7G
1
2
3
4
5
6
7
f-
a
g2
g1
fct
a
f+

 

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
Pout
D
1.4
0.2
150
90
-8.4
13.3
2.2
100,000
1.9
0.7
6%
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated March 30, 2021.
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