The CV1670 is an indirectly heated triode. The prototype was the 4D1. The old GPO code is POVT100B. The STC commercial code is 3A/172B and this exhibit carries both the commercial and the CV Type designations.
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 anode with the control grid visible at the bottom. The grid connects to the top cap by a wire loop to ensure that there is no tension on the glass or electrodes.
Side view of the box anode.
The classic envelope is 38 mm in diameter and, excluding the B7 base pins, is 95 mm tall.
