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Mullard CV66 triode (EC54, RL37)

size This valve measures 74x35mm overall and has a B9G base.

The RL37 was developed by Mullard after STC developed grounded-grid triodes which were superior in performance at 200MHz to the RL7 (EF54). The RL37 was not as good as the STC valve but was more suited to 200MHz circuitry. It was found that an RL37 in front of an RL7 gave around 3.5dB improvement in the overall noise factor (the STC CV53 gave a 4dB improvement) and it was type approved as CV66.

Heater voltage 6.3V
Heater current 0.43A
Max anode voltage 250V
Max anode dissipation 3W
Max cathode current 25mA
Mutual conductance At Va=250V,
Amplification factor 100
Anode impedance 11.1k ohms
Max operating frequency 300MHz
Ca -h+c Measured with spigot connected to grid 0.09pF
Cg - h+c 9.8pF
Cag 7.5pF


Pin Function
1 Heater
2 Grid
3 Grid
4 Anode
5 Anode
6 Grid
7 Grid
8 Cathode
9 Heater
The valve is designed to operate vertically because of the small spacing between grid and cathode. However if it has to be used horizontally it can be provided the spigot key is in a vertical plane.



bottom quarter EC54 markings
A view of the base, plus the Mullard and EC54 markings.

This file was last modified 15:01:48, Tuesday September 02, 2014