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78E

Sensibly equivalent to:
78
See also:
The 'Magic Three' Valves
    
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The 78 and 78E are variable μ RF pentodes. The characteristics presented in the lower box are for the Cossor 78E whilst the first set are for the 78. No data-sheet could be located for the 78E.
The RCA Receiving Tube manual describes the 78 as being electrically identical to the IO based 6K7 apart from the capacitances, thus this is one of the Magic Three valves.
The anode is a solid and grey cylinder inside the bright perforated screen. It is a true pentode with three wire grids.
The classic envelope is 38 mm in diameter, and excluding the UX6 base pins is 100 mm tall.
References: Datasheet, 1040, 4055 & 1043. Type 78E was first introduced in 1935.

 

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

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
6.3
0.3
180
75
-3.0
4.0
-
1.0M
1.10
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated December13, 2013.
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