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AR21 double-diode triode and its equivalent, NR48
AR21 The valve measures 100x28mm overall.


Heater voltage 6.3V
Heater current 200mA
Max anode voltage 300V
Max anode dissipation 1.5W
Mutual conductance Va=250V
Anode impedance 15k ohm
Amplification factor 30
Ca-all 4.8pF
Cg-all 3.9pF
Cag 2.0pF
Cc-all 5.2pF


Pin Function
1 Metallising
2 Heater
3 Anode
4 Diode 1
5 Diode 2
6 no pin
7 Heater
8 Cathode
TC Control grid


Mullard NR48, marked Admiralty Patt. 850, and with the serial number 16789M NR48
Top quarter view Bottom quarter view
Thanks to Andy Carter for providing the AR21.

This file was last modified 15:23:10, Tuesday September 02, 2014