The 12BY7A is a miniature power pentode designed primarily for use as the video output amplifier in television receivers. Features of the tube include extremely high transconductance, low interelectrode capacitances, and high power sensitivity.
Electrically and mechanically, the 12BY7A is replacement for the 12BY7.In addition, however, the 12BY7A exhibits a controlled heater warm-up characteristic which makes the tube particularly suited for use in TV receivers which employ series-connected heaters. When the 12BY7A is used in conjunction with other 600-milliampere types which exhibit essentially the same heater warm-up characteristic, heater voltage surges across the individual tubes are minimized during the warm-up period.