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EL821

Sensibly equivalent to:
6CH6 7D10 CV2127
    
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Type EL821 is a video output amplifier used in professional applications for driving TV or radar signals down (fairly) long cables. We do not think that it was much used, if at all, in domestic sets.
Sources specifically list it as a video amplifier. Note the high value of gm, necessary in order to obtain reasonable gain and power output with wide-band signals, and for correct matching of video into coax cable. TV studio equipment racks used to be full of 6CH6s.
The valve is pin compatible with the 6BW6 but they have different uses.
The anode is mainly closed and prevents a view of the internal structure.
The anode and screens.
See 6CH6 for more information and pictures.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins, is 58 mm tall.
References: Datasheet & 1040.

 

Pin Connections
B9A
1
2
3
4
5
6
7
8
9
ic
g1
k
h
h
-
a
g2
g3

 

Absolute Maximum Operating Conditions
Beam Tetrode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
Pout
D
6.3
0.75
250
250
-4.5
40
6
50,000
11
3W
8.5%
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated April 01, 2014.
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