articles
 
collections
 
timeline
Mullard

ECH81


G8LSD Valve Collection
equivalents
 
new
 
   


home
Sensibly equivalent to:- 6AJ8 - 6C12 - CV2128 - X719
 
See also:
Mullard VHF FM Radio Series Advert, June 1954 - Mullard ECH81 & EF85 Advert, August 1954 - New Valve Assembly Method - Mullard New ECH81, November, 1953
 
This exhibit was last updated on 04 July 2014
Become a friend or
with PayPal.

The ECH81 triode heptode was designed in 1954 for the role of frequency changer (mixer) in superhet receivers for AM reception. The ECH81 acting as oscillator and mixer for AM and the heptode being the first IF amplifier on FM.
The two valve sections share a common cathode. The triode is to be used as the local oscillator feeding the 13 Volts amplitude sine wave to the heptode mixer. Within the heptode, non linear operating causes the signals to interact to produce in the anode waveform the following major frequencies: signal, LO, signal + LO and signal minus LO. The anode circuit is tuned to enhance one of these signals, normally signal minus LO. For radio reception at the time an intermediate frequency of 455 KHz would be typical for AM.
From the side, through the screen, can be seen two sizes of electrodes. Under a glass the lower section can be seen to contain several wire grid spirals. Above the main assembly the cathode continues and a single grid can be seen. Thus the triode is mounted above the mixer on the common cathode tube.
Another ECH81 from the collection. Here the later stylised logo is used and the manufacture is not in the UK.
Looking into the screen the wire grids can be seen. The anode is only fully present in the plane parallel to the cathode.
An enhansed view of the outer grids.
Here the notch and peening method of securing the grid wire can be plainly seen in the outermost grid.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 55 mm tall.
References: 4051 & 1040.
 
Pin Connections
B9A
1
2
3
4
5
6
7
8
9
g2,g4
g1
k,g5,s
h
h
a
g1
a(t)
g1(t)
 
Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
mAa
6.3
0.3
100
13
Heptode
Va
Vs
Vg
mAa
mAs
ra
gm
250
250
-2
6.5
3.8
0.7M
0.775

Thanks to Frank Philipse for supplying the above PDF datasheet
More