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The PL81 was designed for universal mains sets without a mains transformer and with the heaters on a series chain. The parameters given are for a pair in push pull audio service.

As a line output valve in television service, the peak anode surge voltage is 7,000 Volts. The anode dissipation is 8 Watts.

The PL81 can also be used as a series pass element in voltage regulators.

This exhibit is an import and carries the word Foreign. Both inner grids have copper support rods and radiating fins at the top. The cathode is rectangular.

The thin glass tube envelope is 22 mm in diameter and, excluding the B9A base pins, is 72 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type PL81 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.