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The 50CD6 is the 300 mA heater version of the 6CD6G beam tetrode. The parameters given are for single ended audio use with an anode load of 1,500 Ω.

The valve is also specified for push pull service, where it will deliver 13.5 Watts at 1.7% distortion in class A.

Unusually the valve was primarily designed for use as a line output stage in television receivers.

The 50CD6, which is a 'greedy' valve and by no means cheap, would not be a cost-conscious designer's obvious first choice for something as mundane as audio output. The 50CD6 was quite widely used in TVs during the late 1950s. It was often the first valve in the set to fail and very costly to replace.

The anode supply can be 700 Volts, with a positive surge of up to 6,000 Volts. The anode dissipation is 15 Watts and the screen dissipation 3.0 Watts. The anode current can be 170 mA. Other parameters would be a screen voltage of 170 Volts and a negative grid surge of -150 Volts.

The marks on the envelope speak of a hard service life. There are too many leads - in fact there are two separate electrode systems within the anode.

The top view showing one cathode with multiple heater loops. The inner two grids are wound on copper supports. The beam plate support is a rod welded to the side of the bright beam plate.

The classic envelope is 51 mm in diameter and, excluding the IO base pins, is 128 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type 50CD6G was first introduced in 1951. See also 1951 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.