▼ Menu

EF91

Sensibly equivalent to:
5A/160H 5A/160K 6AM6 6F12 8D3 CV138 HP6 SP6 Z77
See also:
EF91 - not the valve that won the war - Television RF Valve Development - Valves and their Habits - Valves for Bands III, IV & V - The EF91 and the Blue Band
    
Extras ▼

 

M-OV who made the Marconi Z77, acknowledged the fact that this valve was universally known by the Mullard designation of EF91 and gave the EF91 top billing on the envelope.
The EF91 is a high gain, high impedance, high slope, screened pentode. Mullard describe the EF91 as primarily intended for use as RF amplifiers or mixer valves in television receivers. At the time, late 1940s, television only operated at VHF.
It could be used from AF to VHF up to about 200 MHz.
The electrodes fill the width of the valve. The anode is formed by two rectangular plates at either side of the valve. The other two sides of the box being completely open. All three grids can be clearly seen.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
References: Datasheet & 1040 Type EF91 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 May 24, 2013.
Return to Main Index