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78

Sensibly equivalent to:
78E A678 AG78 CV2544 G78 UZ-78 UZ78
See also:
The 'Magic Three' Valves
    
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The 78 and 78E are variable μ RF pentodes on the American UX6 base. The RCA Receiving Tube manual describes the 78 as being electrically identical to the later IO based 6K7 apart from the capacitances, thus this is one of the Magic Three valves.
The outer shield hides the inner electrodes.
Looking up from the base, the grids can be seen to be of a significantly smaller diameter than the screen.
The classic envelope is 38 mm in diameter, and excluding the UX6 base pins is 101 mm tall.
References: Datasheet, 1040, 4055 3002, & 1043. Type 78 was first introduced in 1933.

 

Pin Connections
UX6
1
2
3
4
5
6
tc
h
a
g2
g3
k
h
g1

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
6.3
0.3
250
100
-3.0
7.0
1.7
0.8M
1.45
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 04, 2017.
shape:classic construction:pinch type:pentode age:1930.1940 base:ux6 heater:6.3v pins:6 pin:1.h pin:2.a pin:3.g2 pin:4.g3 pin:5.k pin:6.h pin:tc.g1
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