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Z77

Sensibly equivalent to:
6AM6 6F12 8D3 CV138 CV4014 EF91 HP6
See also:
EF91 - not the valve that won the war - Television RF Valve Development - Valves and their Habits - Valves for Bands III, IV & V - Olympia Show 1947 - The EF91 and the Blue Band
    
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The Z77 from M-OV was another designation for the ubiquitous EF91 of the late 1940s. In this exhibit the lettering proclaims a commercial brand of Marconi products. See also Z77 with a paper label.
The design offers high gain, high impedance, high slope, in a screened pentode.
The electrodes fill the width of the valve. The three grids can be clearly seen and all grids have separate pins.
The Marconi Wireless Telegraphy logo.
In this enhanced image shows the form of the anode with joining strap and that all grids are shaped to pass flat across the cathode.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
References: Data-sheet & 1040 Type Z77 was first introduced in 1947.

 

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

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
6.3
0.3
250
250
-2
10
2.5
1M
7.6
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated October 13, 2020.
shape:thin.glass.tube construction:all.glass type:pentode age:1940.1950 base:b7g heater:6.3v pins:7 pin:1.g1 pin:2.k pin:3.h pin:4.h pin:5.a pin:6.g3 pin:7.g2
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