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220DD

 
    
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The 220DD is an indirectly heated double signal diode with a common cathode. It was designed for battery sets using automatic volume control (AVC) now known as AGC (automatic gain control).
Cossor used paper labels to add the Type designation to their valves. The paper is missing but the dome has makers information etched into it. The filament is intact and runs at 2.0 V at 0.2 A.
The electrode assembly showing the anodes, cathode tube, insulated filament and use of mica's top and bottom.
This image shows how the two separate anode plates are wrapped round the cathode.
See also the 1937 DDL4 mains heater double diode.
The balloon envelope is 30 mm in diameter, and excluding the B5 base pins is 75 mm tall.
References: Datasheet4010 & 1043. Type 220DD was first introduced in 1934.

 

Pin Connections
B5
1
2
3
4
5
a(1)
a(2)
f
f
k

 

Absolute Maximum Operating Conditions
Diode
Vh
Ah
Va
mAa
2.0
0.2
20
1.0
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 14, 2013.
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