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805

Sensibly equivalent to:
331A CV625
    
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The 805 transmitting triode is clearly designed for high voltage use, and at reasonable power levels.
The base has four thick stub pins and a locating pip. This points to a bayonet base with spring connections. The valve seems to be a predecessor of the 813 (TT10) tetrode and is probably designed for output power levels of 250 Watts in the HF region of the spectrum.
The graphite anode is 2-3 mm thick. The anode connection to the top cap is via a substantial tape.
The lower ceramic spacer. The grid can be seen to be of significant thickness as in class C RF amplifier service grid current will be drawn on each cycle.
To provide support for the anode, the supports fix to a collar that is tightened around the base of the pinch.
The top ceramic support. The two tension supports each support an inverted V thoriated tungsten filament. In use the filament glows bright orange. At 10 Volts this exhibit takes 3.15 Amps.
The paper label that came with the valve. This was probably from the outside of the original box.
The wide glass tube envelope is 57 mm in diameter and, excluding the base pins, is 193 mm tall.
References: Datasheet & 4061. Type 805 was first introduced in 1936.

 

Pin Connections
1
2
3
4
tc
f
ic
f
g1
a

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
10.0
3.25
1,500
-16
210
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated March 28, 2013.
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