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NR48

Sensibly equivalent to:
AR21 CV1055 EBC33 OM4 VR55
    
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The NR48 is a double diode triode equal to the Mullard EBC33. The type reference indicates a pre CV valve designated for Navy Receiving applications. The envelope carries the words Admiralty Pattern 850 and also the maker's name - Mullard.
The design dates from the late 1930s and the commercial version was part of Mullard's red E series.
The use was at the end of the IF chain where the diodes would demodulate the AM signal and rectify an AGC control voltage, and the triode would act as the first audio amplification stage.
The reverence number 16789M.
The classic envelope is 30 mm in diameter and excluding the IO base pins it is 85 mm tall.
References: Data-sheet, 1040, 1043 & 3002. Type NR48 was first introduced in 1938.

 

Pin Connections
IO
1
2
3
4
5
6
7
8
tc
m
h
a
a(d2)
a(d1)
-
h
k
g1

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
6.3
0.2
250
-5.5
5
15k
2
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated June 10, 2021.
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