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HD24

Sensibly equivalent to:
210DDT AR10 CV1308 CV2985 DDT2 L21DD TDD2A
    
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The HD24 is a directly heated double diode triode that would have been used in broadcast receivers, as detector, AGC detector and first audio amplifier.
This exhibit has a plain glass envelope whereas HD24 has external metalising.
The HD24 has a lower filament consumption than the HD23 which itself was designed to lower the filament consumption and thus replace the HD21 and/or HD22. The HD24 has a lowest anode current rating of the series.
The reverse of the envelope has the Osram sticker.
Although obscured the anode can be made out as a bright box uner the top mica. The two diode anodes appear to form a slim box shape below the triode.
The classic envelope is 44 mm in diameter and, excluding the B5 base pins, is 106 mm tall.
References: Datasheet, 1040 & 1043. Type HD24 was first introduced in 1939.

 

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
0.1
150
-1.5
1.1
28,600
1.4
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated March 19, 2014.
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