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.Mullard also specify the PL81 for use as a series pass element in voltage regulators.
The ceramic insulator is a characteristic of the PL81.
Through the gap in the anode can be seen the bright beam plate and further in are the wire grids. The control grid copper supports are topped with heat dissipating fins.The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 74 mm tall.References: Data-sheet & 1040. Type PL81 was first introduced in 1951. See also 1951 adverts. |
