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EB91

Sensibly equivalent to:
6AL5 6D2 CV140 D152 D77 DD6 EAA91 M8212
See also:
Valves and their Habits
    
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The EB91 is a double signal diode. Mullard separate rectifier diodes and signal diodes in their naming convention. The full wave rectifier being given the letter Z, the twin diodes the letter B.
The EB91 dates from 1949 but the American 6AL5 was produced in 1946. Prior to the EB91 there was the EB41 all glass valve and the EB34.
Mullard designed these diodes for vision and sound detection. Additionally they are recommended for limiting and DC restoration. Each section is internally screened.
The most common fault with the EB91 design is heater to cathode leakage.
This exhibit is British made. The anodes are stitched together.
The two valves are completely separate flat structures separated by a plate screen. This clearly shows the signal usage, where it is important to keep RF isolation.
The makers codes are R31 and B7C.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Data-sheet 1040 & 3002. Type EB91 was first introduced in 1949. See also 1949 adverts.

 

Pin Connections
B7G
1
2
3
4
5
6
7
k(1)
a(2)
h
h
k(2)
s
a(1)

 

Absolute Maximum Operating Conditions
Diode
Vh
Ah
Va
mAa
6.3
0.3
150
9
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 09, 2016.
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