The 6GY8 is a triple triode on a B9A base. It was designed for the purpose of RF amplifier, mixer and AFC in FM receivers. The control grid of triode three is internally connected to the cathode of triode one. The same pin also is used for one side of the heater
The valve is sold by IEC but carries the Mullard name to identify the maker.
The three triode sections mounted side by side.
Thanks to Mike Edwards for the images.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 40 mm tall.
References: Datasheet, 1040 & 1043. Type 6GY8 was first introduced in 1962.
Absolute Maximum Operating Conditions¶
Updated January 03, 2016.