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KT81

Sensibly equivalent to:
7C5
See also:
Olympia Show 1947
    
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The KT81 is the first M-OV kinkless tetrode audio power valve with a pressed glass foot. We can not find details of how it performed in the market place, but it was not a valve produced for many years.
The Marconi paper label. No doubt the Osram valves came off the same production line and differed by only the paper label.
The coating inside the glass obscures almost all of the inner detail. The control grid is wound on copper supports and has heat radiating fins at the top.
See also KT81 for the Osram branded version.
The wide glass tube envelope is 32 mm in diameter and, excluding the B8B base pins, is 70 mm tall.
References: 4018 & 1040. Type KT81 was first introduced in 1947.

 

Pin Connections
B8B
1
2
3
4
5
6
7
8
h
a
g2
ic
ic
g1
k
h

 

Absolute Maximum Operating Conditions
Beam Tetrode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
Pout
D
6.3
0.95
250
250
-4.4
40
7.5
10.8
4.3W
8%
Updated January 20, 2018.
shape:wide.glass.tube construction:all.glass type:beam.tetrode age:1940.1950 base:b8b heater:6.3v pins:8 pin:1.h pin:2.a pin:3.g2 pin:4.ic pin:5.ic pin:6.g1 pin:7.k pin:8.h
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