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2D21

Sensibly equivalent to:
20A3 4G/280K 5121 5727 884 885 ASG5121 CV797 E1955 EN91 G4S2 PL21 PL2D21 QX21 Ste1300/01/05 WT-210-0001
See also:
Mufax Chart Recorder Maintenance Manual - Hewlett Packard 2D21 Box - CV797 short entry
    
Extras ▼

 

The 2D21 thyratron is, as usual, a gas filled valve, in this case the gas at low pressure is xenon. This example is of tetrode construction and was designed for relay or grid-controlled rectifier applications.
Hewlett Packard is a name associated with the very best in electronic instruments but not valve manufacture and this valve was made for HP by General Electric.
When a certain critical anode current flows the ionisation of the gas begins an avalanche discharge that overrides the grid control and leads to saturation current flow. The anode current can then only be extinguished by reducing the anode volts below the ionisation threshold.
The gm value in a normal hard valve is replaced by the control ratio parameter. In this valve the ratio is 250. At saturation the valve voltage drop is 8 Volts.
Side view of the box anode.
The flat face of the anode has been formed with a small flange.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 44 mm tall.
References: Datasheet & 1040. Type 2D21 was first introduced in 1952.

 

Pin Connections
B7G
1
2
3
4
5
6
7
g1
k
h
h
g2
a
g2

 

Absolute Maximum Operating Conditions
Thyratron
Vh
Ah
Va
mAa
6.3
0.6
650
500
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 19, 2018.
shape:thin.glass.tube construction:all.glass type:thyratron age:1950.1960 base:b7g heater:6.3v pins:7 pin:1.g1 pin:2.k pin:3.h pin:4.h pin:5.g2 pin:6.a pin:7.g2
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