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The CV296 (commercial EF55) pentode is physically the big brother of the EF50 with which it shares common base connections.

The CV296 is a single ended RF pentode with very high mutual conductance and a sharp cut-off. The current rating places it as a power valve but it is designated for amplifier service with a medium anode impedance.

The CV173 is also equivalent to the EF55 but there must be a difference between the CV173 and the CV296 for two CV specifications to exist.

The KB/A identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the A identifies the maker as Mullard, Blackburn, pre Jan 1951.

The test sticker from RAF Henlow showing no difference between the two CV specifications.

The wide metal envelope is 33 mm in diameter and, excluding the B9G base pins, is 81 mm tall.

References: Data-sheet & ¹⁰⁴⁰

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.