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The EF93 is a miniature screened pentode on a B7G base. It is a variable μ valve designed for HF use.

The outer screen is connected to g3 at the top and to pin 2 at the base.

The hole in the screen reveals the three helical wire grids within.

The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.

References: Data-sheet, ³⁰⁰² & ¹⁰⁴⁰. Type EF93 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.