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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 KT81 appeared in 1947 and by 1951 this valve was being described as an obsolescent Type.
Produced by M-OV this example is branded Osram and our other KT81 exhibit is branded Marconi.
The detail photograph shows the M-OV identification on the envelope.
The wide glass tube envelope is 31 mm in diameter and, excluding the B8B base pins, is 68 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 13, 2013.
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