The ECC91 is a double triode with a common cathode for use as an RF power amplifier or oscillator. An output power of 1 Watt may be obtained from an ECC91 in a push pull oscillator at 250 MHz. This would involve an anode voltage of 150 Volts and a common grid resistor of 2000 Ω. Each anode would dissipate 1.5 Watts.
Construction features a central cathode with single sided grids and open box rectangular anodes to each side.
Here the control grids can be seen to have been wound conventionally and then one half of the wires has been shaved off.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Data-sheet & 1040. Type ECC91 was first introduced in 1956. See also1956 adverts.
