The CV2021 is a CV493 fitted with tape leads welded to the base pins. The basic valve is the commercial 6X4 HT rectifier.
A common cathode is employed passing through two anodes arranged at right angles to one another.
At 325-0-325 input to the rectifier this will give an HT rail higher than is required for most domestic equipment. Use for audio amplifiers and small transmitters is most probable, or driven at 250 Volts for radio receivers.
The KB/Z identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the Z identifies the maker as MO Valve Company, Hammersmith.
The label identifies this as BS3 but no details have been found.
The KB/Z maker ID plus the original CV493 painted out. Showing the conversion was post production.
A little enhancement makes the CV493 clearer.
The Paxolin carrier for the added welded tapes. The centre cylinder also has a welded tape fitted.
The thin glass tube envelope is 18 mm in diameter and the length, excluding the B7G base pins, is 60 mm.
References: Data-sheet & 1040. Type CV2021 was first introduced in 1953. See also1953 adverts.
