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The Tungsram VO4 is an octode frequency changer or mixer. It was also made with the Ct8 base cap as the VO4s. The specification matches exactly the Mullard FC4 but the envelope is not covered with screening paint in this example.

The oscillator has to generate 12 Volts peak to peak for correct operation. It would typically have used a 90 Volt oscillator anode voltage and up to 2.0 mA anode current. The oscillator would use g1 as control grid and g2 as anode. Of the six grids the final one was a suppressor, g3 and g5 would be screen grids, and the signal would be applied to g4, hence its position as top cap connection.

Thanks to Mark Mallison for sending the images.

The classic envelope is 44 mm in diameter and, excluding the B7 base pins, is 112 mm tall.

References: Data-sheet, & ¹⁰⁴³. Type VO4 was first introduced in 1935. See also 1935 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

PDF scanned from an original document held by the museum