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The AC/SGVM is a variable μ RF tetrode. Initially when released it had a balloon envelope and plastic top cap with screw connection see DC2/SGVM. This exhibit is later and has the top hat top cap and shouldered envelope. It is also fully screened with external metallisation.

The Mazda Valve Manual from 1935 describes the AC/SGVM (and AC/S1VM) as available for replacement purposes. The pentode had taken over from the screened grid valve in their current designs. Their text reads:-

These valves are of the Variable-mu type, solely for use in receivers where volume is controlled by potentiometer adjustment of grid bias. Their characteristics are such that, with increase of negative control-grid voltage, anode current and mutual conductance characteristics follow a shape which minimises cross modulation and amplitude distortion.

The reverse is plain zinc paint.

The classic envelope is 39 mm in diameter, and excluding the B5 base pins is 110 mm tall.

References: Data-sheet, ⁴⁰²², ¹⁰⁴⁰ & ¹⁰⁴³. Type AC/SGVM was first introduced in 1932. See also 1932 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

PDF scanned from an original document held by the museum