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VT51

Sensibly equivalent to:
220PT CV1051 Pen220A
    
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The VT51 battery audio output pentode was capable of 1.1 Watts at 7% distortion.
This specimen is characteristically Cossor shaped and will be a Cossor Type 220PT rather than a Mazda Type Pen220A. Originally designed as audio output pentodes these economical valves found numerous uses in portable battery-powered military transmitters.
The grids are clearly visible within the cylindrical anode. The filament was designed for accumulator use, and the maximum anode voltage of 150 Volts matched the maximum HT batteries available.
The classic envelope is 42 mm in diameter and, excluding the B5 base pins, is 91 mm tall.
References: Datasheet & 1043. Type VT51 was first introduced in 1933.

 

Pin Connections
B5
1
2
3
4
5
a
g1
f-
f+
g2

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
2.0
0.2
150
150
-9
18
3.6
270k
2.2
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 21, 2013.
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