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NR74

Sensibly equivalent to:
AC6/Pen CV1189 PV1-35
    
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This valve is classified as part of the NR series of pre WWII Naval Receiving valves.
This valve is equivalent to the commercial AC6/Pen and was designed for timebase output in early TVs and oscilloscopes. The cathode resistor is given as 90 Ω.
The Type designation uses the - as if it was an American NR-74 but the AM and crown confirm that it is the UK NR74 for Navy Receiving.
The valve is also marked as a CV1189.
The construction used ceramic insulators because of the high voltage involved during flyback.
The Crown and AM for Air Ministry.
The classic envelope is 51 mm in diameter and, excluding the B7 base pins, is 116 mm tall.
References: Data-sheet & 1043. Type NR74 was first introduced in 1938. See also 1938 adverts.

 

Pin Connections
B7
1
2
3
4
5
6
7
tc
nc
g1
g2
h
h
k
nc
a

 

Absolute Maximum Operating Conditions
Beam Tetrode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
4.0
1.75
310
210
-6.9
63
14
8.5

 

Absolute Maximum Operating Conditions
Beam Tetrode
Pdriv
Pout
freq
f.max
1.0W
73W
20MHz
60MHz
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated March 11, 2025.
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