42 Facts About Vacuum tubes

Vacuum tubes tube, electron tube, valve, or tube, is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.

Thermionic Vacuum tubes are still used in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, amplifiers for electric musical instruments such as guitars, as well as high end audio amplifiers, which many audio enthusiasts prefer for their "warmer" tube sound.

Gas-filled Vacuum tubes are similar devices, but containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases, usually without a heater.

Tubes have different functions, such as cathode-ray Vacuum tubes which create a beam of electrons for display purposes in addition to more specialized functions such as electron microscopy and electron beam lithography.

Early Vacuum tubes used the filament as the cathode; this is called a "directly heated" tube.

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Since the tube contains a vacuum, the anodes in most small and medium power tubes are cooled by radiation through the glass envelope.

The solid-state device which operates most like the pentode tube is the junction field-effect transistor, although vacuum tubes typically operate at over a hundred volts, unlike most semiconductors in most applications.

The many scientists and inventors who experimented with such Vacuum tubes include Thomas Edison, Eugen Goldstein, Nikola Tesla, and Johann Wilhelm Hittorf.

The high-vacuum tubes could operate at high plate voltages without a blue glow.

Later circuits, after Vacuum tubes were made with heaters isolated from their cathodes, used cathode biasing, avoiding the need for a separate negative power supply.

Vacuum tubes showed that the addition of an electrostatic shield between the control grid and the plate could solve the problem.

Beam power Vacuum tubes offer the advantages of a longer load line, less screen current, higher transconductance and lower third harmonic distortion than comparable power pentodes.

Beam power Vacuum tubes can be connected as triodes for improved audio tonal quality but in triode mode deliver significantly reduced power output.

Early Vacuum tubes used a metal or glass envelope atop an insulating bakelite base.

Miniature Vacuum tubes became predominant in consumer applications such as radio receivers and hi-fi amplifiers.

Bare tungsten filaments remain in use in small transmitting Vacuum tubes but are brittle and tend to fracture if handled roughly—e.

Directly heated cathode Vacuum tubes continued to be widely used in battery-powered equipment as their filaments required considerably less power than the heaters required with indirectly heated cathodes.

Vacuum tubes used as switches made electronic computing possible for the first time, but the cost and relatively short mean time to failure of tubes were limiting factors.

The quality of the Vacuum tubes was a factor, and the diversion of skilled people during the Second World War lowered the general quality of Vacuum tubes.

Advances using subminiature Vacuum tubes included the Jaincomp series of machines produced by the Jacobs Instrument Company of Bethesda, Maryland.

Colossus was the first use of vacuum tubes working in concert on such a large scale for a single machine.

Elimination of silicon from the heater wire alloy allowed the production of Vacuum tubes that were reliable enough for the Whirlwind project.

The 7AK7 Vacuum tubes improved the cathode poisoning problem, but that alone was insufficient to achieve the required reliability.

Considerable amount of heat is produced when Vacuum tubes operate, from both the filament and the stream of electrons bombarding the plate.

High-power amplifier Vacuum tubes are designed with external anodes that can be cooled by convection, forced air or circulating water.

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Internal elements of Vacuum tubes have always been connected to external circuitry via pins at their base which plug into a socket.

Subminiature Vacuum tubes were produced using wire leads rather than sockets these were restricted to rather specialized applications.

Later, consumer Vacuum tubes were given names that conveyed some information, with the same name often used generically by several manufacturers.

Some special-purpose Vacuum tubes are constructed with particular gases in the envelope.

For instance, voltage-regulator Vacuum tubes contain various inert gases such as argon, helium or neon, which will ionize at predictable voltages.

However, some large transmitting Vacuum tubes are designed to operate with their anodes at red, orange, or in rare cases, white heat.

Vacuum tubes tube needs an extremely high vacuum to avoid the consequences of generating positive ions within the tube.

Early gettered Vacuum tubes used phosphorus-based getters, and these Vacuum tubes are easily identifiable, as the phosphorus leaves a characteristic orange or rainbow deposit on the glass.

Large transmitting Vacuum tubes have carbonized tungsten filaments containing a small trace of thorium.

Cathodes in small "receiving" Vacuum tubes are coated with a mixture of barium oxide and strontium oxide, sometimes with addition of calcium oxide or aluminium oxide.

Cathode depletion was uncommon in signal Vacuum tubes but was a frequent cause of failure of monochrome television cathode-ray Vacuum tubes.

Vacuum tubes can be tested outside of their circuitry using a vacuum tube tester.

Traveling-wave Vacuum tubes are very good amplifiers and are even used in some communications satellites.

High-powered klystron amplifier Vacuum tubes can provide hundreds of kilowatts in the UHF range.

At one time many radios used "magic eye Vacuum tubes", a specialized sort of CRT used in place of a meter movement to indicate signal strength or input level in a tape recorder.

In general, vacuum tubes are much less susceptible than corresponding solid-state components to transient overvoltages, such as mains voltage surges or lightning, the electromagnetic pulse effect of nuclear explosions, or geomagnetic storms produced by giant solar flares.

Vacuum tubes are still practical alternatives to solid-state devices in generating high power at radio frequencies in applications such as industrial radio frequency heating, particle accelerators, and broadcast transmitters.