The CV1931 is the glass GT version of the commercial 6H6 valve family. This valve has pinch construction that adds to the length of the envelope and has space above the electrode assembly making it twice the length of the metal version.
This exhibit is a double diode. The diodes are low voltage low current signal rectifiers and not suitable for power supply service. The low current is reflected in the low heater power.
The KB/FB identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the FB identifies the maker as STC, Footscray.
Face view of one diode. The envelope also carries the commercial Type designation of 6H6GT.
The heaters are in series and bridged at the top.
A closer view.
The wide glass tube envelope is 28 mm in diameter and excluding the IO base pins the valve is 59 mm tall.
