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N78

Sensibly equivalent to:
6BJ5 CV3711 CV4062
    
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The N78 is a 1953 audio output pentode with a high mutual conductance, suggesting that full output can be obtained with a low input signal.
In class AB1 push pull a pair of valves can deliver 9 Watts at 4.5% distortion. If connected as triodes the pair can deliver 6.3 Watts at 1.6% distortion.
M-OV produced these valves and branded them with paper labels: GEC for professional sales and commercially, Emitron, Marconi and Osram.
The Osram label.
The suppressor grid support can be seen through the hole in the end of the anode. The support is notched by a pointed disc cutter, the wire is dropped into the groove and finally a flat ended disc pushes the displaced metal back and this locks the wire in place.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 59 mm tall.
References: Datasheet & 1040. Type N78 was first introduced in 1952.

 

Pin Connections
B7G
1
2
3
4
5
6
7
g1
k,g3
h
h
a
ic
g2

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
Pout
D
6.3
0.64
250
250
-5.5
36
5
40,000
10
4W
10%
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated April 29, 2018.
shape:thin.glass.tube construction:all.glass type:pentode age:1950.1960 base:b7g heater:6.3v pins:7 pin:1.g1 pin:2.k.g3 pin:3.h pin:4.h pin:5.a pin:6.ic pin:7.g2
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