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EF50. In the field of electronics, the EF50 is an early all-glass wideband remote cutoff pentode designed in 1938 by Philips.It was a landmark in the development of vacuum tube technology, departing from construction techniques that were largely unchanged from light bulb designs. [1]
Ordinary pentodes are referred to as sharp-cutoff or high-slope pentodes and have uniform aperture size in the control grid. The uniform construction of the control grid results in the amplification factor (mu or μ) and transconductance changing very little with increasingly negative grid voltage, resulting in fairly abrupt cutoff of plate ...
The EF86 [1] is a high transconductance sharp cutoff pentode vacuum tube with Noval (B9A) base for audio-frequency applications. It was introduced by the Mullard company in 1953 [2] and was produced by Philips, Mullard, Telefunken, Valvo, and GEC among others. It is very similar electrically to the octal base EF37A and the Rimlock base EF40.
In electronics, cut-off is a state of negligible conduction that is a property of several types of electronic components when a control parameter (that usually is a well-defined voltage or electric current, but could also be an incident light intensity or a magnetic field), is lowered or increased past a value (the conduction threshold).
For signal pentodes, an odd numerical identifier most often identified a variable transconductance (remote-cutoff) valve whereas an even number identified a 'high slope' (sharp-cutoff) valve. For power pentodes and triode-pentode combinations, even numbers usually indicate linear (audio power amplifier) devices while odd numbers were more ...
1A4-p – Remote-cutoff pentode; 1A4-t – Remote-cutoff tetrode; 1A6 – Pentagrid converter up to only 10 MHz due to low heater power (2 V/60 mA) and consequent low emission in the oscillator section; also occasionally used as a grid-leak detector; 1B4-p – Sharp-cutoff pentode; 1B4-t – Sharp-cutoff tetrode; 1B5 – Dual detector diode ...
EF41/6CJ5 (62VP) – Remote-cutoff pentode, EF4, EF22/7B7 or EF39/6K7 with a Rimlock base; EF42 – Pentode, EF52 with a Rimlock base; EF43 – Remote-cutoff pentode; EF50 (EF53) – Remote-cutoff pentode for use in the IF stages of 1940s TV and radar receivers, B9G 9-pin Loctal base ; EF51 – Remote-cutoff pentode; EF52 – Pentode, EF42 with ...
The 954 and 956 types are sharp and remote cut-off pentodes, respectively, both also with indirect 6.3 V, 150 mA heaters. Types 957, 958 and 959 are for portable equipment and have 1.25 V NiCd battery heaters. The 957 is a medium-μ signal triode, the 958 is a transmitting triode with dual, paralleled filaments for increased emission, and the ...