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The CV3991 (4X150D) has a heater rated at 26 Volts for working off of 24 Volt vehicle supplies. The 4X150A differs only in having a 6.3 Volt heater.

The 4CX150D beam tetrode is a close relative to the 4CX250B VHF/UHF RF power output valve and has the same finned anode structure. The silver plated fins are contained in an outer ring, and in use air would be forced over the fins for anode cooling. A special base and chimney were designed for the purpose.

The spigot connects to the control grid g1 the base ring to the screen grid g2 and the finned top section (radiator) to the anode.

The base is a glass disc with pins protruding through. The evacuation seal is covered by a central metal spigot.

The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.

The base pins set in hard glass and spigot. For forced air cooling there is copper ribbon between the central anode and outer ring. A special base and chimney directs air up from the base and exhausts above the anode.

The co-axial glass envelope is 32 mm in diameter and, excluding the B8F base pins, is 45 mm tall.

Reference: Data-sheet. Type CV3991 was first introduced in 1954. See also 1954 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.