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CV1581

Sensibly equivalent to:
ECH35
    
Extras ▼

 

The CV1581 is a triode hexode and the prototypes were the ECH35 and E1341. The old RAF service code is VR99A.
The advantage of the separate oscillator is resistance to oscillator 'pulling' on strong signals, something that the heptode was prone to.
This exhibit has little internal coating and the structure can be seen.
The KB/DA identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the DA identifies the maker as Mullard Radio Valve Co., Blackburn.
The triode hexode mixer occupies the top of the envelope with the much smaller triode oscillator below.
All the hexode grids are wire of differing diameters and pitches.
The triode oscillator with copper control grid supports. The cathode is common with the mixer. The heater wire is an insulated coil.
The classic envelope is 34 mm in diameter and, excluding the IO base pins, is 96 mm tall.
Reference: Data-sheet. Type CV1581 was first introduced in 1940. See also 1940 adverts.

 

Pin Connections
IO
1
2
3
4
5
6
7
8
tc
m
h
a
g2,g4
g1(t),g3
a(t)
h
k
g1

 

Absolute Maximum Operating Conditions
Hexode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
6.3
0.3
250
100
-2.0
3.0
3.0
1.3M
0.65

 

Absolute Maximum Operating Conditions
Triode
Va
mAa
100
3.3
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated August 01, 2025.
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