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TDD2A

Sensibly equivalent to:
AR10 CV1308 CV3726 HD24 L21DD
    
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The TDD2A is a double diode triode for battery receivers. The function was as detector, AGC rectifier and first audio voltage amplifier in a superhet broadcast receiver.
We also have the earlier balloon bulb TDD2A version.
This exhibit has the modern top cap that was introduced in the early/mid 1930's. The filament is a single inverted V held at the top in a tension spring. The anode is a rectangular box and the grid wire passes flat across the filament. With the triode at the top the diodes must be near the pinch.
See also TDD2A for a more squat shaped version.
The top mica and edge of the anode can just be seen in this image.
The classic envelope is 40 mm in diameter, and excluding the B5 base pins is 104 mm tall.
References: Datasheet, 1040 & 1043. Type TDD2A was first introduced in 1934.

 

Pin Connections
B5
1
2
3
4
5
tc
a
a(d1)
f(-)
f(+)
a(d2)
g1

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
2.0
0.12
135
-1.5
1.95
25,000
1.2
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated November 06, 2013.
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