During the Second World War the British electronics industry was working flat out to meet demand for components for the emerging field of electronic warfare with everything from radios to radar needing valves and other components. The British could not produce enough pieces to meet demand so the War Department looked to the electronics manufacturers of the United States to help meet the shortfall and tonight we are looking at an American made valve produced for the British in the form of the CV788:

This vlave is made from glass and is particularly short and dumpy compared to most British valves. This particular valve is a ‘dual transmitting tetrode’ apparently and the online resource ‘The Valve Museum’ offers this description of the valve:

The design is of the American type with two separate valves sealed into the single element. Additionally the valve is probably of American manufacture as the envelope bulge is characteristic. The oval cylinder anodes enclose the beam plates, grids and heater cathode assembly. This type of construction usually required external capacitors to neutralise parasitic oscillations. These normally being vertical wires alongside the envelope.This valve was obsolete by the start of the 1960s replaced by the QQV03-20 or QQV06-40A varieties. It is typical of these RF power tetrodes that the base connections all match one another.The wide glass tube envelope is 56 mm in diameter and, excluding the B7A base pins, is 52 mm tall.

The base of the valve has seven base pins arranged in a circle:

The valve’s designation and a broad arrow ownership are printed on the glass:

My thanks go to Michael Fletcher who kindly spotted this valve for me, picked it up and swapped it with me for some kit I didn’t want!