0
0Z4 - Full-Wave Gas Rectifier
1 Volt heater/filament tubes
1L6 - Pentagrid converter
2 Volt heater/filament tubes
2B7 - Twin-diode remote-cutoff pentode
5 Volt heater/filament tubes
300B - 40 Watt directly heated triode
5Y3
5751 - low voltage low-noise avionics tube
6 Volt heater/filament tubes
6AQ5 - (EL90)
6AU6A - (EF94)
6BQ5 - (EL84)
6C19
6CA7 - (EL34)
6CL6 - Power pentode
6DA6 - (EF89)
6DJ8 - (ECC88)
6J5
6L6 - (EL37)
6N3P
6SK7 - Remote-cutoff pentode
6SN7 - Medium-mu twin triode
6V6 - Beam power tube (see also: 5V6 and 12V6)
12 Volt heater/filament tubes
12AT7 - High-mu twin triode (ECC81)
12AU7 - Medium-mu twin triode (ECC82)
12AV6 - Twin diode/High-mu triode (see also: 6AV6)
12AX7 - High-mu twin triode (ECC83)
12BA6 - Remote cutoff pentode (See also: 6BA6)
12BE6 - Pentagrid converter (See also: 6BE6)
12DT6 - Sharp cutoff pentode
25 Volt heater/filament tubes
25L6
50 Volt heater/filament tubes
50B5 - Beam power tube
50C5 - Identical to 50B5 except for biasing arrangement (HL92)
50L6 - Beam power tube (see also 25L6)
50HK6 - Power pentode
2/12/08
American designation (with European equivalents)
Field emitter vacuum tubes
In the early years of the 21st century there has been renewed interest in vacuum tubes, this time in the form of integrated circuits. The most common design uses a cold cathode field emitter, with electrons emitted from a number of sharp nano-scale tips formed on the surface of a metal cathode.
Their advantages include greatly enhanced robustness combined with the ability to provide high power outputs at low power consumptions. Operating on the same principles as traditional tubes, prototype device cathodes have been constructed with emitter tips formed using nanotubes, and by etching electrodes as hinged flaps (similar to the technology used to create the microscopic mirrors used in Digital Light Processing) that are stood upright by a magnetic field.
Such integrated microtubes may find application in microwave devices including mobile phones, for Bluetooth and Wi-Fi transmission, in radar and for satellite communication. Presently they are being studied for possible application to flat-panel display construction.
Information from Wikipedia.
Other vacuum tube devices
A vast array of devices were built during the 1920–1960 period using vacuum-tube techniques. Most such tubes were rendered obsolete by semiconductors; some techniques for integrating multiple devices in a single module, sharing the same glass envelope have been discussed above, such as the Loewe 3NF. Vacuum-tube electronic devices still in common use include the magnetron, klystron, photomultiplier, x-ray tube and cathode ray tube. The magnetron is the type of tube used in all microwave ovens. In spite of the advancing state of the art in power semiconductor technology, the vacuum tube still has reliability and cost advantages for high-frequency RF power generation. Photomultipliers are still the most sensitive detectors of light. Many televisions, oscilloscopes and computer monitors still use cathode ray tubes, though flat panel displays are becoming more popular as prices drop.
The fluorescent displays commonly used on VCRs and automotive dashboards are actually vacuum tubes, using phosphor-coated anodes to form the display characters, and a heated filamentary cathode as an electron source. These devices are properly called "VFDs", or Vacuum Fluorescent Displays. Because the filaments are in view, they must be operated at temperatures where the filament does not glow visibly. It is relatively easy to create highly customized VFD display designs, with all the legends required for a specific task. These devices are often found in automotive applications, where their high brightness allows reading the display in daylight.
Some tubes, like magnetrons, traveling wave tubes, carcinotrons, and klystrons, combine magnetic and electrostatic effects. These are efficient (usually narrow-band) RF producers and still find use in radar, microwave ovens and industrial heating.
Gyrotrons or vacuum masers, used to generate high power millimetre band waves, are magnetic vacuum tubes in which a small relativistic effect, due to the high voltage, is used for bunching the electrons. Free electron lasers, used to generate high power coherent light and perhaps even X rays, are highly relativistic vacuum tubes driven by high energy particle accelerators.
Particle accelerators can be considered vacuum tubes that work backward, the electric fields driving the electrons, or other charged particles. In this respect, a cathode ray tube is a particle accelerator.
A tube in which electrons move through a vacuum (or gaseous medium) within a gas-tight envelope is generically called an electron tube.
Some condenser microphone designs use built-in vacuum tube preamplifiers.
As of 2008, scores of small companies are manufacturing audiophile amplifiers and preamps that use vacuum tubes.[4]
Vacuum tube can also mean a tube with a vacuum. It is e.g. used for demonstration of, and experiments with, free-fall.
Information from Wikipedia.
Cooling
All vacuum tubes produce heat while operating. Compared to semiconductor devices, larger tubes operate at higher power levels and hence dissipate more heat. The majority of the heat is dissipated at the anode, though some of the grids can also dissipate power. The tube's heater also contributes to the total, and is a source that semiconductors are free from. Caution should be used in handling heated tubes, as the temperature of the glass may be high enough to easily and quickly burn the skin, even with low-power miniature tubes.
In order to remove generated heat, various methods of cooling may be used. For low power dissipation devices, the heat is radiated from the anode—it often being blackened on the external surface to assist infrared radiation. Natural air circulation or convection is usually required to keep power tubes from overheating. For larger power dissipation, forced-air cooling (fans) may be required.
From the inception of this technology until the 1950s, the dominant approach to cooling low power tubes remained aimed at avoiding immediate or very short term failures. For noncritical consumer applications, and in absence of technological alternatives, tube failures did not create major problems for equipment manufacturers, as the cost of tube replacements was borne by end users long accustomed to the experience. Some tubes for the US defense market featured a metal casing, as opposed to glass, and an opaque, black finish that facilitated both heat conduction and radiative cooling. In some highly specialized professional applications where replacement was out of the question, such as undersea cable repeaters, no failures were acceptable. Moreover, as vacuum tube based defence systems became increasingly complex and deployed in ever increasing numbers, it became clear that point failures which were individually easy to diagnose and rectify had a devastating effect on the uptime of systems that contained tens, hundreds, and especially thousands of tubes. This resulted in both the creation of special long lasting tubes for projects such as Whirlwind and SAGE, and also in special tube shields that aided heat dispersal and could be retrofitted on existing equipment. These shields act by improving heat conduction from the surface of the tube to the shield itself by means of tens of copper tongues in contact with the glass tube, and have an opaque, black outside finish for improved heat radiation.
High-power tubes in older, large transmitters or power amplifiers are liquid cooled, usually with deionised water for heat transfer to an external radiator, similar to the cooling system of an internal combustion engine. Since the anode is usually the cooled element, the anode voltage appears directly on the cooling water surface, thus requiring the water to be an electrical insulator. Otherwise the high voltage can be conducted through the cooling water to the radiator system; hence the need for deionised water. Such systems usually have a built-in water-conductance monitor which will shut down the high tension supply (often tens of kilovolts) if the conductance becomes too high. Some very high-power transmitters, such as those used in shortwave broadcasting and VLF communications, use pressurized steam for cooling. Modern transmitters using tubes mainly in the PA section are now largely cooled by forced air through a radiator or other heat-sinking device.
Information from Wikipedia.
Applications
Vacuum tubes are less susceptible to the electromagnetic pulse effect
of nuclear explosions. This property kept them in use for certain military applications long after transistors had replaced them elsewhere. Vacuum tubes are still used for very high-powered applications such as microwave ovens, industrial radio-frequency heating, and power amplification for broadcasting. Many audiophiles, professional audio engineers, and musicians prefer the characteristics of audio equipment based on vacuum tubes over electronics based on transistors. Because this tube sound is so sought after there are many companies which still make specialized audio hardware featuring tube technology. Tubes are still being manufactured today in China (Shuguang), Russia (Reflector Corp. and Svetlana Electron Devices), USA (Westrex Inc.) and Slovakia (JJ-Electronic).The characteristic s
ound produced by a tube based amplifier with the tubes overloaded (overdriven) is widely used in electric guitar amplification, and has defined the texture of some genres of music, such as classic rock and blues. Guitarists often prefer tube amplifiers for the perceived warmth of their tone and the natural compression effect they can apply to an input signal.In 2002, computer motherboard maker AOpen brought back the vacuum tube for modern computer use by releasing the AX4GE Tube-G motherboard. This motherboard uses a Sovtek 6922 vacuum tube as part of AOpen’s TubeSound Technology. AOpen claims that the vacuum tube brings superior sound.
Information from Wikipedia.
World War II
Near the end of World War II, to make radios more rugged, some aircraft and army radios began to integrate the tube envelopes into the radio's cast aluminum or zinc chassis. The radio became just a printed circuit with non-tube components, soldered to the chassis that contained all the tubes. Another WWII idea was to make very small and rugged glass tubes, originally for use in radio-frequency metal detectors built into artillery shells. These proximity fuzes made artillery more effective. Tiny tubes were later known as "subminiature" types. They were widely used in 1950s military and aviation electronics.
Information from Wikipedia.
Whirlwind
To meet the unique reliability requirements of the early digital computer Whirlwind, it was found necessary to build special "computer vacuum tubes" with extended cathode life. The problem of short lifetime was traced to evaporation of silicon, used in the tungsten alloy to make the heater wire easier to draw. Elimination of the silicon from the heater wire alloy (and paying extra for more frequent replacement of the wire drawing dies) allowed production of tubes that were reliable enough for the Whirlwind project. The tubes developed for Whirlwind later found their way into the giant SAGE air-defense computer system. High-purity nickel tubing and cathode coatings free of materials that can poison emission (such as silicates and aluminum) also contribute to long cathode life. The first such "computer tube" was Sylvania's 7AK7 of 1948. By the late 1950s it was routine for special-quality small-signal tubes to last for hundreds of thousands of hours rather than thousands, if operated conservatively. This reliability made mid-cable amplifiers in submarine cables possible.
Information from Wikipedia.
Colossus
The Colossus computer's designer, Dr Tommy Flowers, had a theory that most of the unreliability was caused during power down and (mainly) power up. Once Colossus was built and installed, it was switched on and left switched on running from dual redundant diesel generators (the war time mains supply being considered too unreliable). The only time it was switched off was for conversion to the Colossus Mk2 and the addition of another 500 or so tubes. Another 9 Colossus Mk2s were built, and all 10 machines ran with a surprising degree of reliability. The only problem was that the 10 Colossi consumed 15 kilowatts of power each, 24 hours a day, 365 days a year—nearly all of it for the tube heaters
Information from Wikipedia.
Receiving tubes
Cathodes in small "receiving" tubes are coated with a mixture of barium oxide and strontium oxide, sometimes with addition of calcium oxide or aluminium oxide. An electric heater is inserted into the cathode sleeve, and insulated from it electrically by a coating of aluminum oxide. This complex construction causes barium and strontium atoms to diffuse to the surface of the cathode when heated to about 780 degrees Celsius, thus emitting electrons.
Information from Wikipedia.
Transmitting tubes
Large transmitting tubes have tungsten filaments containing a small trace of thorium. A thin layer of thorium atoms forms on the outside of the wire when heated, serving as an efficient source of electrons. The thorium slowly evaporates from the wire surface, while new thorium atoms diffuse to the surface to replace them. Such thoriated tungsten cathodes routinely deliver lifetimes in the tens of thousands of hours. The claimed record is held by an Eimac power tetrode used in a Los Angeles radio station's transmitter, which was removed from service after 80,000 hours (~9 years) of uneventful operation. Transmitting tubes are also claimed to survive lightning strikes more often than transistor transmitters do. For RF power levels above 20 kilowatts, vacuum tubes are commonly more efficient and reliable than similar solid-state circuits.
Information from Wikipedia.
Vacuum
Vacuum
It is very important that the vacuum inside the envelope be as perfect, or "hard", as possible. Any gas atoms remaining might be ionized at operating voltages, and will conduct electricity between the elements in an uncontrolled manner. This can lead to erratic operation or even catastrophic destruction of the tube and associated circuitry. Unabsorbed free air sometimes ionizes and becomes visible as a pink-purple glow discharge between the tube elements.
To prevent any remaining gases from remaining in a free state in the tube, modern tubes are constructed with "getters", which are usually small, circular troughs filled with metals that oxidize quickly, with barium being the most common. While the tube envelope is being evacuated, the internal parts except the getter are heated by RF induction heating to extract any remaining gases from the metal. The tube is then sealed and the getter is heated to a high temperature, again by radio frequency induction heating. This causes the material to evaporate, absorbing/reacting with any residual gases and usually leaving a silver-colored metallic deposit on the inside of the envelope of the tube. The getter continues to absorb any gas molecules that leak into the tube during its working life. If a tube develops a crack in the envelope, this deposit turns a white color when it reacts with atmospheric oxygen. Large transmitting and specialized tubes often use more exotic getter materials, such as zirconium. Early gettered tubes used phosphorus based getters and these tubes are easily identifiable, as the phosphorus leaves a characteristic orange or rainbow deposit on the glass. The use of phosphorus was short-lived and was quickly replaced by the superior barium getters. Unlike the barium getters, the phosphorus did not absorb any further gasses once it had fired
Information from Wikipedia.
