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AC/HLDD

Sensibly equivalent to:
11A2 A234 CV2813 DDT4 DDT DH42 H4D MHD4 TDD4
    
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The AC/HLDD is an indirectly heated double diode triode for mains superhet receivers. It was designed for signal and AGC detection and then as the first post detection amplifier.
The reverse is plain zinc loaded screening paint.
The classic envelope is 44 mm in diameter and, excluding the B7 base pins, is 107 mm tall.
References: Datasheet & 1043. Type AC/HLDD was first introduced in 1933.

 

Pin Connections
B7
1
2
3
4
5
6
7
tc
a(d2)
m
a(d1)
h
h
k
a
g1

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
ra
gm
4.0
1.0
250
13,800
2.6
PDF scanned from an original document held by the museum
Updated October 14, 2018.
shape:classic construction:pinch type:triode age:1930.1940 base:b7 heater:4.0v pins:7 pin:1.a(d2) pin:2.m pin:3.a(d1) pin:4.h pin:5.h pin:6.k pin:7.a pin:tc.g1
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