The 12BY7A is a 1950s video amplifier output valve designed for boosting wideband TV video signals to a sufficiently high level to be transmitted over a considerable length of cable without loss of quality.
The heater is rated for 12.6 volt use and is centre tapped. Makers describe the 12BY7A as a pentode but the construction is as a beam tetrode. The 7054 has the same base connections and looks to be the same visually, however, the 7054 is designed for transmitter use and lacks the heater centre tap and has different characteristics.
Henning Hertz comments that the 12BY7A was widely used by radio amateurs in the 1960's and 1970's as a driver stage for a pair of 6146B tetrodes in the PA (final stage) of HF transmitters up to 30 MHz.
One side of the pressed anode, the strap in integral to the anode pair.
The rectangular opening in the bright beam plate, copper grid support and screen grid winding. The grid passes flat across the cathode.
The anodes have extra central flanges for additional heat dissipation.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 59 mm tall.
References: Data-sheet, 1040 & Henning Hertz. Type 12BY7A was first introduced in 1955. See also1955 adverts.
