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The VR65A/SP41 is an amplifier pentode with external metallisation as shielding. The 4.0 V heater was common in the 1930s when mains sets first began to appear.

This is an example of a War-surplus valve resprayed and rebranded in the 1960s by a London-based dealer in order to make the valve look brand new and worth the price charged. Inside is a 1940s Mazda-made VR65A, originally spray-coated in grey and marked for military use.

Very large numbers of these valves were sold for next-to-nothing on the Surplus market in the late 1940s but, since they were by then obsolescent and had little use in Civvy Street, most of them just lay in store for the next 20 years.

However, by the 1960s they were again in limited demand for maintaining ex-Services test equipment (oscilloscopes, etc.) which was then popular in Amateur circles, and in Third-World countries.

By this time the stored valves were looking tatty (spray paint discoloured and peeling, etc.) so Z & I Aero Ltd, of Tottenham Court Road invested in some snazzy red paint to rejuvenate their ageing stock! To be fair, however, most of the valves supplied were unused and probably as good as when they were made.

The classic envelope is 31 mm in diameter and, excluding the MO base pins, is 78 mm tall.

References: Private communication, data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type VR65A was first introduced in 1938. See also 1938 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.