Vacuum tube identification
In January,a group of collector-historians interested in the use, history, and preservation of electron tubes and electron tube technology formed the Tube Collectors Association TCA. The Bylaws of the TCA are located here. The Tube Collectors Association is established to support and encourage the collection of electron tubes of all types and historical periods. The TCA provides a forum for sharing information on the development, manufacturing, trends in design, specifications, and historical relevance of electron tubes.
The membership of TCA is dedicated to the non-commercial collection of electron tubes and the preservation of electron tube history. Jim Cross jim vacuumtubesinc. Norm Wilson, N6JV n6jv n6jv. TCA members receive our magazine, Tube Collectora bi-monthly publication filled with both technical and historical information relevant to electron tubes, much of which is not widely known or would require extensive research to find.
In addition, Tube Collector reports on the current market value of collectable electron tubes and electron tube-related items such as literature, tube testers, and unique hardware. Finally, Tube Collector includes a non-commercial "Buy-Sell" list for use by members. For more on Tube Collectoruse the "our magazine" link to your left. TCA has an email reflector, open to members and others. It is a handy way to identify "mystery tubes" and communicate with other Collector-historians.
To join, simply send a blank, untitled email to: tubecollectorsassociation-subscribe yahoogroups. The TCA is the current caretaker of the Perham-Eimac Archive The Perham-Eimac Archive consists of 48 shelf-feet of Eimac tube manufacturing information from to plus several cabinets of legal and miscellaneous information.
Please contact Ludwell Sibley if interested in using these archives. The TCA was granted permanent c 3 status as a non-profit organization by the IRS, and as such we would be greatly interested in donations of tube-related archival material. Please contact Ludwell Sibley if you have such material you wish to donate. Our membership is rapidly growing and we invite you to join. Instructions are available on the TCA membership application. TCA now accepts payments via! Identify your payment to: tca jkasystems.
You may also apply online using this membership application. If you have questions or suggestions for the web page, please contact Norm Wilson: n6jv n6jv. Director John Atwood jgatwood one-electron. Director Jim Whartenby antqradio sbcglobal.A vacuum tubean electron tube   or valve British usage or, colloquially, a tube North America is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
Tube Cross-reference and Selection Guide.
The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a heated cathode and is used for a number of fundamental electronic functions such as signal amplification and current rectification.
Non-thermionic types, such as a vacuum phototube however, achieve electron emission through the photoelectric effectand are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode invented in by John Ambrose Flemingcontains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode.
Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids. They were crucial to the development of radio, television, radar, sound recording and reproductionlong-distance telephone networks, and analogue and early digital computers.
Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics. In the s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable, durable, safer, and more economical than thermionic tubes.
Beginning in the mids, thermionic tubes were being replaced by the transistor. However, the cathode-ray tube CRT remained the basis for television monitors and oscilloscopes until the early 21st century.
Thermionic tubes are still used in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, and amplifiers that audio enthusiasts [ who? Gas-filled tubes are similar devices, but containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gasesusually without a heater.
One classification of thermionic vacuum tubes is by the number of active electrodes.
A device with two active elements is a diodeusually used for rectification. Devices with three elements are triodes used for amplification and switching. Additional electrodes create tetrodespentodesand so forth, which have multiple additional functions made possible by the additional controllable electrodes.
Tubes have different functions, such as cathode ray tubes which create a beam of electrons for display purposes such as the television picture tube in addition to more specialized functions such as electron microscopy and electron beam lithography.
X-ray tubes are also vacuum tubes. Phototubes and photomultipliers rely on electron flow through a vacuum, though in those cases electron emission from the cathode depends on energy from photons rather than thermionic emission. Since these sorts of "vacuum tubes" have functions other than electronic amplification and rectification they are described in their own articles.
Vacuum Tube Basics
A vacuum tube consists of two or more electrodes in a vacuum inside an airtight envelope. Most tubes have glass envelopes with a glass-to-metal seal based on kovar sealable borosilicate glassesthough ceramic and metal envelopes atop insulating bases have been used.
The electrodes are attached to leads which pass through the envelope via an airtight seal. Most vacuum tubes have a limited lifetime, due to the filament or heater burning out or other failure modes, so they are made as replaceable units; the electrode leads connect to pins on the tube's base which plug into a tube socket. Tubes were a frequent cause of failure in electronic equipment, and consumers were expected to be able to replace tubes themselves.
In addition to the base terminals, some tubes had an electrode terminating at a top cap. The principal reason for doing this was to avoid leakage resistance through the tube base, particularly for the high impedance grid input.
Other reasons for using a top cap include improving stability by reducing grid-to-anode capacitance,  improved high-frequency performance, keeping a very high plate voltage away from lower voltages, and accommodating one more electrode than allowed by the base. There was even an occasional design that had two top cap connections.
The earliest vacuum tubes evolved from incandescent light bulbscontaining a filament sealed in an evacuated glass envelope. When hot, the filament releases electrons into the vacuum, a process called thermionic emissionoriginally known as the "Edison Effect". A second electrode, the anode or platewill attract those electrons if it is at a more positive voltage. The result is a net flow of electrons from the filament to plate.
However, electrons cannot flow in the reverse direction because the plate is not heated and does not emit electrons.All Rights Reserved. Built with Volusion. Join our mailing list! When the single character codes were used up, double character codes were introduced. For example, the 6SN7 has two cathodes, two grids, two plates, and a filament. Additional letters: A Controlled heater warmup time, although can also be used to denote increased ratings or performance over and above the non-A model.
C Ditto. G Glass bulb. GT Glass tubular. W Ruggedised version. X Low loss ceramic base. Y Low loss phenolic base. What does J. Sylvania was a major manufacturer of Military tubes and selected a 3 digit lettering system to designate Sylvania products.
One system prefixes a three-digit number with the letters "VT", presumably meaning "Vacuum Tube". The numbers following these prefixes can be special four-digit numbers, or domestic two- or three- digit numbers or simply the domestic North American RETMA numbering system.
Like the British military system, these have many direct equivalents in the civilian types. Confusingly, the British also had two entirely different VT nomenclatures, one used by the Royal Air Force and the other used by the General Post Office, responsible for post and telecommunications at the time, where it may have stood for Valve, Telephone; none of these schemes corresponded in any way with each other.
Havells Sylvania is an international designer and manufacturer of lighting products. It has plants throughout Europe, Asia, North Africa and Central and South America, and is one of the few lighting companies that produces both lamps and lighting fixtures.
It is owned by Havells. Founded in the early s as a business that renewed burned-out light bulbs, Sylvania and its predecessor companies ultimately began producing new lamps and then vacuum tubes for the radio industry.
Especially, during the 's war effort, it was a common practice for USA factories to source tubes from each other and re-label them.Identifying unmarked tubes? Posted: Jan Mon 10, pm. I have a bunch of tubes with the numbers completly rubbed off. How do I go about figuring out what they are?
Some have numbers on the base which I assume are part numbers so is there a reference for that? Well, if absolutely everything else fails, you can look at the tube itself and the pattern of pins in the base to get close. Here's an example: I found myself with a totally unmarked S globe tube.
It had a 5-pin base, no top cap, and the plate was the main element visible inside the glass. So I figured it was a triode. I set my tube tester up as a 27 and tested. So I tried it as a 37 and it tested good. So that's how I marked it. The base pattern matched a 6F6. So I tested it that way. It tested good. So that's what I think it is. Two big plates, and a base pattern that looks like a smiley face.
Paul- the older 2. That should also aid in determing what is what. However, all bets are off when it comes to 6C5G tubes. I have used many metal ones over the years and imagined their internal structure was just about like a 6J5, but they aren't.
The 6C5 looks like a tube that started out as a pentode and would with all the grids tied together to make it a triode. I was so used to looking at particular element structures of tubes in the boxes that I have and that one really threw me a curve. Posted: Jan Tue 11, am. Remember guys, I'm strictly a neophyte at this. I don't know an s from an st nor even what those designations mean. I need a less technical approach if possible. Maybe compare it to a marked one that looks the same and set the tester for that?
Is there a cross reference for the numbers on the base? There's no cross reference, it's just manufacturing-plant and date coding, completely meaningless for identifying the tube. You could try it, just make sure you start the filament voltage at the lowest setting and turn it up until the needle swings into the "good" range.
I think maybe identifying unmarked tubes is just one of those things you just learn with experience. Get side and base pictures and put some known tube next to the unknown one, to give a sense of scale. Often you can bring the numbers back long enough to read them by putting the tube in the freezer for a few hours, then carefully looking it over at an angle in relatively bright light quickly after removing from the freezer.
The 6C5 was made from a pentode, and will fool you every time just by looking at the internal structure. I have a dream, or perhaps a fantacy.
There could be a tube-tester looking thing that hooks up to a personal computer.The vacuum tube business was a very incestuous one, so much so that you can rarely trust everything that is printed on a tube. Often, the printed brand or printed country is incorrect. Vacuum tubes were simply a commodity that everyone needed like batteries or light bulbs are today. For the most part, back then no one cared when a tube was made or who made it, they just wanted a good product that would work and bring their radio, amplifier or TV back to life.
Which is part of the reason it can be so hard to figure out today. There were a few different reasons a given company would re-brand or write the wrong country of origin on a tube. They ran out of stock of one particular type and contracted another company to make them to fulfill an order.
This is why you see even major brands like Sylvania with RCA date codes. If they could source the tubes cheaper than they could manufacture them. Ironically, European tubes like Telefunken and Mullard were seen as inferior to US tubes at the time as they were cheaper and many tubes you will see an RCA labeled tube that was really produced by Telefunken.
When trying to identify a tube it makes the most sense to first determine where it was made. This is important for two reasons. Depending on where it was made, you there are different clues to look for. Once you know where it was made, that narrows down the possible manufacturers by a lot.
The first place to start is to look for EIA or Manufacturer codes. When in doubt, these code should be given the most weight in your determination. There is much more to say about EIA and date codes which we have reserved for another article.
If you find the tube in North America, assume the European code is correct. If you find the tube in Europe, assume the USA code is correct. USA codes will always be in the form of 3 or 4 numerical digits. European codes can be a bit more difficult to decipher. Typically, European codes are printed a chalky, easily rubbed off type of paint towards the bottom of the tube near the pins.
Once you've seen this type of paint it's easy to spot. While the codes are usually at the bottom, we have seen these codes in other places like the bottom of the base. Euro codes usually have two lines, the first consisting of 3 or 4 digits and the second almost always having just three digits. Much can be deciphered from these codes but that's for another article.
We specialize in new-old-stock tubes and offer high quality tubes, sockets, capacitors, and other parts. Owner Jim Cross and his knowledgeable staff continue to offer the same great expertise and service. Categories can be browsed, but for tubes, it is probably easiest to enter your tube type number in the "search" box. We are continuously adding special types and brands.
Tubes are of various old stock brands, unless otherwise noted. We are constantly searching for tubes and other parts to replenish our stocks.
Please Click Here for a list of the tubes we are currently buying and our bid prices. Also feel free to call us if you think you might have collectible types or other tubes or tube testers we might be interested in.Vacuum Tubes Basics: 10 things you need to know
Vacuum Tubes, Inc remains open during the corona virus concern. While many businesses are in "lockdown", we are exempt as we do almost all of our business via mail order. We are fortunate that none of our family has yet been touched by the illness, and we pray for good health and healing for all and a speedy return to normalcy. We are about to enter the 21st century with new use of social media. Be watching for twitter, facebook, instagram, and youtube content in the near future.
We sell some of the rare and special items we receive on eBay to reach the widest audience possible. Our ebay ID is not surprisingly vacuumtubesinc. Please Click Here to visit our eBay store. Your shopping cart is empty. My Cart. You have no items in your shopping cart. Enter your email to sign up for our newsletter:.
Vacuum Tubes, Inc Sligh Blvd.Tube Pin Identification - IowaPhilco - How do I know from a schematic which pins are which on the tube socket sitting in the chassis? The heater pins are easy to identify because of continuity testing and they seem to be larger diameter but what about the others?
I can't always trust tracing the circuit because the radio came to me non functioning and the circuitry doesn't appear to be correct in some instances when looking at the schematic.
Is there a clock position that's always constant or something? It will give you a diagram of the tube with the pin numbers.
One is to whip out your handy dandy tube manual and look it up. Some schematics have the pin numbers indicated on them some not. I think you maybe be asking how do I count pins on the bottom of a tube? Older standard base tubes: 4, 6, and 7 pin tube are simple. Face them towards you. The pin on the left is pin 1 count clockwise to determine the others.
For instants a 4 pin tube pin 1 is the fat pin to the left. Pin 2 is the thin one above it. Pin 3 is the thin pin to the right of pin 2. And pin 4 is the other fat one. On the 5 pin tube two of the pins are closer together.
Pin 1 is the one on the left of two that are closer together, pin 5 is the one to the right of pin1. Schematics that don't pin numbers doesn't mean that the connections are layed out in the order in which they appear on the schematic. I see I'm late to the party!
Identifying Vintage NOS Vacuum Tubes by Brand Country and EIA Code
Yup, I've got a "bullet" - the one with the oval dial glass. It's been a fun restore so far.
I can tell by the materials used and the methods of repair that it's had multiple people working on it over the last 80 years. Some of the repairs are sloppy by my standard so I'm trying to clean up things. Thank you for the education on this. Are you saying with your last sentence that if the schematic, like the one I posted, doesn't have the pins numbered that I can't necessary refer to that layout? Stated another way. I suppose I should refer to the materials shared above as the "gospel" truth for that tube pin layout.
The RCA Triple Pindex is, by far, the most easiest and concise index to use for tracking down pin numbers. Take a look at it I'll get back to the bench with these materials.