Additional manu codes 2014 04

I n fo rm a t io n a b o u t Va c c u m Tu b e s Fa c t o ry c o d e s EI A/ RETMA a n d ty pe c o de s Am p e re x , Mu lla rd , P h ilip s e t c .

Principles of tube testing Rev.1 2013

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For those who uses NOS valves in the equipment.

S o m e t im e s is it d if f ic u lt t o g e t a ll t h e a n s w e r a n d t h is c o v e r n o t a ll in f o rm a t io n

This is a collection and only a little start help for decoding factory codes and dates.

But this don’t tell you all, because many manufacture didnt code there components And there can be difficult to decode because of changed codes during the years.

(And the re c a n be faults in the he lp g uide whic h I’m no t is re s po ns ible fo r.)

S o urc e s and informatio n: BK pre c is io n http://www.bkprecision.com/

David Kott http://www.greenbulletmics.com/VACUUM_TUBES.html N. V Philips The Bre nt Je s s e e Re c o rding & S upply, Inc http://www.audiotubes.com/ Udo Radtke , http://www.tubecollection.de/ TESLA codes http://www.radiojournal.cz/tab1.htm Link to read ; http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm CONTENTS

Pag e

1. Where to Get Them 2. Choosing the Right Tubes for Your Amp 3. Getting to Know Tubes 4. Buying Tubes on Auction Sites 5. (NOS) New Old Stock Tubes 6. How to Identify Used Tubes 7. Identifying NOS Tubes 8. Matching Tubes 9. Buyer Beware!

10. ADDITIONAL MANUFACTURER EIA/RETMA CODES (US tandard) 11. EIA codes for US made electronic components 12. Deciphering the Manufacturer's Production Code 13. Mullard EL34 production codes 14. Amperex, Mullard, Philips, and Valvo Tube Codes 15. Philips code 16. Telefunken codes 17. And about those codes 18. The European code 19 The American code 20. CV codes 21. Codes US VT(Valve Tube)JAN joint Army Navy 22. Valve Numbers and how to decode them 22. PRINCIPLES OF TUBE TESTING: 23. List of Valve Names and Manufacturer from 194324. EL 34 variants 25. EIA RETMA Chassis Wiring Color Code 26. TESLA codes 27. Brimar codes 28. Russian tube eq.

29. Information

3 3-4 5 5 6 6 7 7-9 10 11-15 15-24 25 26 27-31 32-46 47-48 49 49 50 50-53 53 54-59 60-68 69-71 72-74 75 76-102 103-104 105 -108 109

Always remember that there are le t h a l v o lt a g e s inside a Vacuum tube amplifier that can kill you just as dead as a bolt of lightning! So make sure that you know exactly what you’re doing before you attempt to do anything inside the chassis of your amp!

NOS means new old stock, ANOSmeans almost new old stock, =OS old stock used NIB means a new tube in the original box.

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Fo re word

VACCU U M TU BES by www.greenbulletmics.com David Kott W h e re t o Ge t Th e m I wanted to put in this section about buying tubes because many beginners have no idea where to acquire good tubes. The are not so many countries producing vacuum tubes today (Russia, China, and Slovak Republic.)

Tubes are not made in the United States anymore, so to get n e w o ld s t o c k ( N O S ) US made tubes, you'll have to look to tube sellers who have a supply of NOS tubes, or look to auction sites where tons of tubes can be found, or simply check out garage and estate sales (you'd be surprised!). Favorite place to find NOS tubes is at hamfest’s. Hamfest’s as I mentioned before have nothing to do with pork. They are usually one day flea markets where amateur radio operators gather to sell their wares. Many sellers are long time radio operators, who were into radio back when all radio equipment was made using tubes. You can usually find lots of new and used tubes at a fraction of the cost that you'll pay on auction sites and from tube dealers.

You can find a number of amp related websites that sell parts that also sell tubes.

There are also many websites devoted to selling tubes only that can be found by doing a simple search using the usual search engines. You will find that the prices will vary widely from one place to another, so shopping around will save you a lot of money, especially on the expensive high end European tubes such as the Mullards, Telefunken's, and others made in Hungary, Germany and Great Britain, as well as the more expensive US made tubes.

Ch o o s in g t h e Rig h t Tu b e s f o r Yo u r Am p Choosing the right tubes is important to getting good tone from your amp. Choosing different types and even different brands can affect the tone of your amp. It's a good idea to learn how to identify new tubes from used tubes, or tubes that are slightly used from tubes that have seen a lot of use if you're going to venture out and buy tubes at hamfest’s and such. If you go to hamfest’s, you'll find some people with huge boxes full of loose tubes. I usually avoid those as the tubes are usually pretty well banged up and will likely be noisy.

I look for the sellers who have the tubes boxed up and have a list of all the tubes they have on hand. I would advise you to know which type, and brands you want to buy before you start shopping. This is because there are so many different types of the same number tube out there that you may get confused and end up with something different than what you thought you were getting. For instance, let’s say you set out to buy a set of 12AU7 low gain preamp tubes. There are a number of tubes that have different numbers on them, but in fact are the same tube, for example, a 12AU7, and a 12AU7A. They are the same tube, but one has an A at the end. This simply means that the one with the A at the end is a newer tube. Tube mfg.'s changed, or added something to some tube numbers throughout time, so it's important to know which tubes you can use, and which ones you can't. In this example, the 12AU7 and the 12AU7A are the same tube, you can use either one without any electronic changes being made and both have the same gain factor.

There are also the JAN tubes, in which JAN stands for " Jo in t Arm y N a v y ", that use totally different numbers for almost all common tubes. The very same 12AU7 in a military number may be referred to as a 6189, or a 5814A, but it's just the same as a 12AU7 tube. Military tubes will usually have "JAN" printed right on the tube along with the tube number, or, a military tube may also have the letters "W A " following the tube number, for example 12AU7WA. This is not a different tube, but rather a military tube. Military tubes are usually built better to withstand the rugged conditions that they may be put through. They also usually have been put through a "burn in" period before being boxed and labeled for military use. You may see a burn spot on the silver part of the tubes, which is called the “ f la s h in g ”, that may give the

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tube a used appearance, but is usually just a sign that the tube was burned in before being put into use. It does not mean the tube is used. A vacuum tube is most likely to fail, if it's going to fail, in the first 48 hours of use, and this is one of the reasons that military tubes are burned in. It also stabilizes the tube electronically and burns up any air or gasses that don't belong in the tube.

But let’s say you're looking for a rectifier tube. Let’s say you're looking for a 5U4G rectifier tube for your 59 bassman. You will find that there are also tubes labeled as 5U4GA, or 5U4GB. Some tubes may have both of these numbers on them. Although you can usually use a 5U4GA, or a 5U4GB in place of a 5U4G, they are different electronically, and if you had a 5U4G in your amp and you replaced it with a 5U4GB, you may need to have the bias adjusted if it is adjustable. In this example, a 5U4G and a 5U4GA are not the same tube. The 5U4GA and 5U4GB have different plate voltages and will change the amount of voltage going to the rest of the components in your amp. Although it's not likely to cause any damage to your amp, it will affect the bias, and the way the amp will sound.

So as you can see, it's important to know exactly what you're looking for before setting out to buy tubes. It's a good idea to learn the military equivalents of the tubes you use too because they are usually superior tubes, and can sometimes be purchased for less than the regular production tubes. It's a good idea to make a list of the tubes you need and their equivilants before you set out to buy tubes at a hamfest. If you're like me, you won't remember all the military and industrial equivilants while you're out looking around!

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Ge t t in g t o Kn o w Tu b e s I'm not going to get too deep into tubes because there is just way too much to learn if you really want to get into how tubes work and affect tone, but I think it's important to know how to get the most out of your tubes and how to select the right tubes for the tone that you want to get. If you want to learn more about tubes, there are a number of good books and websites that can help you to understand tubes better. One good book that I have read and would recommend to anyone who wants to get some really good general information on tubes is titled, " Ge t t in g Th e Mo s t O u t o f Va c u u m Tu b e s ", and is written by Robert B.Tomer. This book gives information on tube types, causes of tube failure, selecting tubes, what to expect from tubes, how to identify noisy tubes, testing methods, different types of testers, getting the most from your tubes, and all about tube maintenance. It's not a book for technicians, but rather the average Joe who just wants to learn a little about using and maintaining tubes and tube equipment. It's available at the Antique Electronics Co. website. It's a great book that I'd highly recommend to anyone.

B u y in g Tu b e s o n Au c t io n S it e s A word of caution to those of you who prefer to use auction sites rather than buying from a tube dealer or venturing out to hamfest's and garage sales. There are literally hundreds of people selling new and used tubes on auction sites. Many of them are people who found a box full of tubes cleaning out their attic. Others are people who buy tubes at estate sales and other places, and resell them on the auction sites. Some are even people who buy certain tubes on auction sites only to put them back on to resell them at a higher price.

Unfortunately, some tube sellers are not completely honest with their buyers, especially on auction sites. There are also many very reputable tube sellers who are honest, and describe their tubes as they truly are. The trick is finding them. These sellers usually have tested the tubes and list all the tubes readings, and guarantee the tubes to be as described. Many will even take returns if you are not 100% satisfied with the tubes. These are the people you want to deal with on auction sites. Be cautious of buying " a s is " tubes. Personally, I wouldn’t buy any “as is” tubes.

On the other hand, I have found out the hard way that there are many dishonest tube sellers on the auction sites who often will clean up decent looking used tubes, put them in a box and sell them as new old stock. Trust me, I have more than my share of used NOS tubes! These sellers usually don't give an accurate description, and may or may not say they are tested and list test results. However, almost all these sellers will have in big bold letters, " N O RETU RN S ", and do not guarantee the tubes at all. Stay away from tubes in white boxes that are said to be NOS, unless they are the original white military boxes which will have print on the boxes identifying them, or, unless they are guaranteed and returnable. Some sellers will even find factory boxes and put used tubes of the same type and brand in them. Watch out for crossed out tube types on the boxes. This always indicates that the box is not the tubes original box.

Do not buy tubes from sellers who will not give you a refund if the tubes they sell don't work or check out to be as advertised. It's sad to say, but I think there are more scammers than there are honest tube sellers on auction sites. One thing you should always do with anyone you buy tubes from is to c h e c k t h e ir f e e d b a c k . If you see anything that throws up a red flag, move on to another seller. If you see dissatisfied tube buyers giving negative feedback, move on to another seller. You will be able to tell the honest tube sellers from the scammers usually by the feedback, and the good sellers will always be happy to answer all your questions and send you close up pictures if you request them.

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( N O S ) N e w O ld S t o c k Tu b e s w it h o rig in a l b o x e s ( N I B ) N e w in B o x n o rm a lly re p a c k e d in a w h it e b o x When looking for new old stock tubes, always look for tubes that have their original factory boxes. Most actual NOS tubes will have them. Sometimes the tubes are very old, and the boxes will be in rough shape. This is common, but make sure the box and tube type on the box match the type of tube in the box. Sometimes a seller will put tubes with damaged boxes into new white boxes, but will usually have the original box for you to see. Most reputable sellers will do this if the factory boxes are shot, but will tell you. It has been my experience that sellers who actually have NOS tubes will guarantee them to be so, and will take them back if you have any doubts. These are the sellers to deal with.

I don't buy NOS tubes from anyone who doesn't guarantee them to actually be NOS anymore.

I have actually seen tubes with heat marks on the bases of tubes, which is the result of many, many hours of use, actually advertised as NOS. You must be careful who you buy from when buying tubes on auction sites.

H o w t o I d e n t if y U s e d Tu b e s Some of the things to look for that indicates that tubes have been used are burn marks, which may appear as dark spots on the silver part of the glass tube, called the " f la s h in g " of the tube. The tube’s flashing is the first place to look for signs of use. Also look for a halo of colors around a spot of flashing. If you see a tube that has very little flashing, or any white parts of the flashing, this indicates a tube with gas, or a loss of vacuum. Do not buy tubes with white on the flashing!

Also look for darkening around the base of tubes with light brown bases, on the base of the tube where it meets the glass. If the edge of the base looks darker than the rest of the base, it’s caused by heat, which indicates many hours of use. Look for scrapes on the tube bases as well that are left from tube holders, or butterfly clamps that hold the tubes securely in place in amps. Look for heat cracks in the base as well. Heat cracks will appear as very fine hairline cracks in the base, which may be hard to see so look closely. Heat cracks usually indicate a very well used tube.

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I d e n t if y in g N OS a n d N I B Tu b e s N e w o ld s t o c k (NOS)tubes in original boxes,N e w in B o x ( N I B ) re p a c k e d in w h it e b o x e s , are tubes made years ago that have not yet actually been used. They should have bright shiny flashing with no signs of burns or discoloration, or halo's around it, with the exception of military tubes which may show burn in markings. Military Tubes will usually show a small burn spot on the flashing from being " b u rn e d in " before being boxed for military use. The bases of new tubes should be clean and free of scrapes and scratches from tube holders.

Most NOS tubes will also have the silk screening on the glass in good condition, meaning the tube mfg logo, and usually the tube type and date code. This stuff does come off easily on some tubes, so don't be discouraged if a tube has a lot of it missing. It can be wiped off by simply taking the tube out and putting it back in the box or even wiping it gently with your fingers. So don't be discouraged if a tube has much of the silk screening missing as long as the tube looks good otherwise.

Sometimes white, or light colored lettering on the glass part of a tube will darken from heat, so if you see a tube which has the lettering on it discolored, or possibly turned a light brown, this will indicate use. Also look at the tubes pins. The pins on a new tube should all be straight and not bent. Sometimes you can even see markings on the pins from being inserted into a tube socket, but don't judge a tube solely on this because most NOS tubes being sold have been tested and may show some scrapes on the pins. Pay more attention to bent pins, but keep in mind that the pins do bend fairly easily, so bent pins doesn't always mean the tube is used.

You may even find NOS tubes with broken lo c a t o r p in s . The locator pin is the big fat pin on the base of the tube that is a molded part of the base. It has a key shape so that the tube can only be inserted into the socket when the locator pin is properly lined up with the hole in the tube socket. Buying tubes with broken locator pins is N O T a good idea. Although a broken locator pin will not affect a tubes performance, all it takes is installing the tube in the wrong position one time to possibly cause a lot of damage to your expensive amplifier, so it's a good idea to avoid those.

Once you've seen a few actual new tubes, and a bunch of used tubes, and have examined each closely, you'll be able to easily tell which tubes are new and which aren't.

Ma t c h in g Tu b e s Matching tubes is something that everyone who uses tubes should know a little about. Sometimes it is not necessary to have matched tubes, but many times it is best to have matched tubes. I won't get into this subject too deep because there is too much to learn, but I will touch on some basics.

For the most part, it's only necessary for your amp's p o w e r t u b e s to be matched.

Preamp tubes are mostly self biasing, and do not require matching although some audiophile's insist that their preamp tubes be matched from side to side. Most preamp tubes have two sides, and are kind of like having two tubes in one. Having the two sides matched perfectly is not necessary.

On the other hand, power tubes are not (normally) self biasing, and sometimes it is best to have tubes that are matched for certain parameters in order for your amp to work more efficiently, and to produce cleaner tone. Sometimes people prefer to have their power tubes mismatched a bit which will make the amp distort more, or sooner.

Having perfectly matched tubes will make your amp sound cleaner than having mismatched tubes.

Power tubes are usually matched for two main parameters. One being the TRAN S CO N D U CTAN CE of the tube, sometimes written as Gm , which is the overall strength of the tube, and a reading that gives you an idea of how used, or new a tube may be. Tubes are measured for Gm on most good tube testers, which also test tubes for shorts, gas, and grid leakage. Each different type of tube has a given transconductance measurement that it must meet in order to be considered a "good" tube, which is determined usually by the tube mfg., although most tubes of the same type no matter what the brand is will have the same parameters that they must meet to be considered a good tube. Tube testers that do not read a tubes transconductance, but merely give you a "GOOD" or "BAD" reading, are not a good

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way to test a tube. They are very inaccurate, and can even damage a good tube by applying AC voltage to the tube where it shouldn't be. These are the tube testers we used to see commonly in drug stores and hardware stores years ago, and luckily, are not seen very often these days.

The other, and more important parameter when matching tubes up for an amplifier, is the tubes plate CU RREN T D RAW , which is measured in milliamps ( m A's ), and is the measurement of current that the tubes draw from the circuit when at idle, or, when the amp is on but not in use. This measurement is actually the tubes bias reading, and should be within the tube mfg's recommended specifications. Again, like tube types usually have a certain range that they should be within no matter what the brand.

Each power tube will draw a different amount of current even though it may be the same type as the other, or others, which is determined by its individual internal construction. For instance, you can have two 6L6 power tubes that are identical, and even have the same mfg. and date code, but one may draw 25 milliamps, and the other may draw 38 milliamps in the same circuit. Again, with current draw, there are certain specifications given by the tube mfg. that these tubes should meet. These parameters are all different for different types of tubes. In the case of a US made 5881, the mfg. may state that the tube should draw anywhere from 20 to 36 milliamps at idle (amp on, but not being used). The tubes can be safely run anywhere within those specs, but if they are run below the minimum, will not perform properly and may make an amp sound muddy, and if ran too far over the upper limit, will run very hot and if run too high, the plates may actually get red hot and the tube will burn up very rapidly. With the high cost of NOS power tubes these days, I don't think you'll want this happening.

For a pair of tubes to be truly matched, there are also other factors that should be checked too, but for a pair of tubes to be considered matched, they should be at least matched for transconductance and current draw. The current draw at idle is what we also refer to as b ia s . When we rebias an amp, what we adjust, if the amp has an adjustable bias, is the current draw of the power tubes at idle. For a pair, or a quad set of tubes to be "matched", the Gm (transconductance) should be very close from tube to tube, and the current draw should be within a few milliamps from one tube to the other, or others. Some people will say within 8 milliamps, others will say 4 milliamps is acceptable, but in general, the closer, the better if you want your tubes to be matched.

When a pair of tubes are properly matched in a push-pull type amplifier, each tube will be doing about the same amount of work. When the tubes are mismatched, one tube will be working harder than the other, thus likely causing one tube to go bad before the other. Using tubes that are mismatched can also have some advantages to those who want their amps to distort. Having tubes that are not matched well will cause an amp to distort more, or sooner than an amp with tubes that are evenly matched. So, some people will purposely install mismatched tubes to get their amps to distort more. Some people will have individual bias pots (adjustor) for each power tube installed in their amps, so that they can either match mismatched tubes in the amp by adjusting the amount of current each tube draws to be the same to get a cleaner tone, or, mismatch matched tubes to draw different amounts of current to increase the amount of distortion that the amp produces.

Whichever way you set them, they should all be set within the mfg's limits. When buying tubes on auction sites that are advertised as being matched, 90% of the time they are not matched at all. Most of the tubes that are tested on half way decent tube testers are only tested for transconductance (Gm), and many people match tubes for this and advertise them as being "perfectly matched" when in reality, they are not because most tube testers do not test tubes for current draw. The ones that do, usually do not test them under actual working voltages and therefore may not give you accurate readings.

Believe it or not, I have seen people advertise tubes as being matched because they are the same type and brand, and have the same date code, or, because they come in matching boxes. So if you're looking for matched tubes, you'll have to get them either from one of the companies who do match tubes, or from one of the few tube

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sellers on the auction sites who actually have the right equipment to do so if you don't have the means to match them up yourself, which you can do if your amp is set up so that you can safely check the bias with a digital volt meter.

You can buy well matched tubes from certain companies that usually re-label the tubes they sell and put their company name on them, but these places rarely sell US made NOS tubes, and if they do, you'll be paying top dollar for them, and you'll usually have to ask for NOS tubes if you don't want current production Russian or Chinese tubes. Personally, I go for the NOS tubes but I get them at hamfest’s and other places at a fraction of the cost and test and match them myself.

If you have an amp with a f ix e d b ia s (not adjustable), you may be forced to buy tubes that have been tested for current draw for your amp to work properly, but many amps can be modified to have an adjustable bias. Having an adjustable bias will allow you to find the bias setting that gives you the best tone with your amp, but you will need to do your homework to learn to do it safely and properly.

For guitar players, running your tubes low, or cold, will prolong the life of the tubes but may result in a muddy tone. Running them high, or, hot, will generally give you better tone, but will reduce the life of the tubes. You'll need to experiment with your amp to see what setting you like best. (One good thing about playing harp, is that you don't need to run tubes real hot as many guitarists do to get good tone because lower bias settings will make your amp distort sooner, and, make the tubes last longer too!

You can also have your amp set up so that you can read the current that each power tube is drawing with a common volt-ohm meter. This will also allow you to match up your output tubes for current draw under actual working conditions if you have a bunch to work with, or mismatch them purposely if you'd like a little extra distortion.

There are also tools available that you insert between the amp and the tube that will allow you to take a bias reading with a volt meter if your amp is not set up to be able to read the bias otherwise.

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B u y e r B e w a re !

There are plenty of NOS tubes to be had on the auction sites, so learn how to identify them and deal only with people who guarantee their tubes. This way you can’t go wrong and get ripped off. Check feedback. This is your first clue to the seller’s reputation. Most buyers don’t have testers so you need to rely on these sellers being honest. The ones who accept returns are the ones you can usually count on to actually have NOS tubes.

B EW ARE o f t h e s c a m m e rs . There are unfortunately, a lot of them out there. If you’d rather look into current production tubes, or buy from companies who resell new tubes under their own names, keep in mind that these companies, who put their company names on tubes do not actually produce the tubes. They are either NOS, or, more likely current production tubes that have been collected and tested, matched up into pairs or quads, and sold at huge profits. Most of these tubes are not US made tubes. They are either Russian or Chinese tubes that are likely inferior to vintage US made tubes. You may be able to get NOS US made tubes through these companies, but you’ll probably have to ask for NOS US made tubes and pay high prices for them.

Tubes usually do not go bad over time if kept in the right environment, and some of the best tubes ever made were made back in the 40’s, 50’s, and 60’s when tubes were used in almost all electronics. The mfg’s kept the quality control at much higher standards than they did in the later years when transistors and solid state electronics started coming into play. I use tubes made in the 40’s and 50’s and they work just fine and have great tone. Military tubes are a good choice. They are usually heavy duty tubes that are less noisy than regular production tubes and are usually built to handle rough usage.

I don’t usually use any current production tubes, but I have tried some of the EL84’s made by JJ Tesla Electronics, which is a Russian plant. These tubes have a nice warm tone and sounded good in my Blues Jr. Amp. I have been hearing good reports on the JJ tubes, so if you want to buy current production tubes, I would say try the JJ Tesla’s if anything, and stay away from Chinese tubes for now (I’ve heard that they’re stepping up on quality, but that’s yet to be seen).

Recently, a Russian plant has bought the Tung Sol name and is producing tubes labeled as Tung Sol. One particular tube of interest is the new 5881 power tube. The plant is producing a ”re-issue” of the highly sought after US made Tung Sol 5881 which is one of the best 5881 tubes ever made. They were made with a rugged mica support system which kept them from becoming noisy over their usable life. They were also known for their warm vintage tone, and ability to break up sooner than other 5881’s and 6L6 tubes, which are basically the same tube except for some slight electrical differences. The original US made Tung Sol 5881’s are the tubes that came as the stock power tubes in the original 1959 Fender Bassman amp’s, and are part of the reason for their infamous tone.

The Russian made re-issue Tung Sol 5881’s are being made in much the same way as the original’s with the extra mica supports and the same type plates. They also have the same short brown base and short bottle shape. The only real noticeable physical change is the tubes ”getter” which is located at the top of the tube like the originals, but unlike the original windmill type getters, the new tube has a single round disc getter. So far, the re-issue Tung Sol 5881’s are getting pretty good reviews by most tube dealers and amp builders. If they prove to be anywhere near as good as the original US made Tung Sol 5881, they will be a great buy at $45 to $50 a pair and a much needed addition to the currently available line of new production power tubes.

Go o d lu c k a n d h a p p y t u b e h u n t in g !

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CODES ADDITIONAL MANUFACTURER EIA/RETMA CODES (US tandard) There are several ways of identifying a manufacturer, or particular part number of a component in most audio gear that’s been manufactured since the mid 1950s. There’s an EIA (Electronic Industries Association) code that identifies the manufacturer, or company, sometimes stamped (either in ink, or metal embossing, or ID tag) on the particular component –( in this case the transformer). Sometimes there is also another series of numbers stamped on the piece, this is the OEM (Original Equipment Manufacturer) part numbers above or below the EIA code, and in some cases parts makers elected not to include the EIA codes, so not all parts have them. These ”Code” formats were not completely standardized, but a little deciphering will generally yield the info that’s needed to identify the transformer in question. For example if you have 606-432 on a transformer, you can tell that it’s a Schumacher transformer from the ’606’, the year is either 1974, or a 1964, from the ’4’, and the ’32’ is the week of production. The model type, or number, is sometimes stamped on the transformer frame, or bell, as well; for example 022798, telling us that this is the power transformer from a Fender Super Reverb Code 24 67 73 101 102 106

Manufacturer Becker Eminence J.B. Lansing (JBL) Admiral Aerovox Corp.

Allen Bradley

109

American Condensor

Capacitors

111 119

Amperex

Tubes Speakers Tubes, Speakers Speakers Speakers Potentiometers, Resistors, Capacitors Potentiometers, Speakers, Resistors Transformers Connectors, Sockets Potentiometers, Resistors Tranformers Speakers Speakers Radios Tubes Sockets Tubes Capacitors Speakers Transformers Resistors, Potentitomers Wire Capacitors Transformers Speakers RF Equipment

125 130 132 134 137 138 139 140 141 145 150 152 158 160 162 163 169 172 173 175 178 183 185 187

Automatic Manufacturing Bendix Panasonic/Matsushita Talk- A-Phone Centralab CTS Stancor (Chicago Standard) Cinch-Jones Clarostat Ensign Coil Consolidated/Cinaudagraph Crescent Crosley DuMont Eby Eimac/Eitel-McCullough Aerovox Hi-Q Division Hitachi Ensign Coil Erie Essex John E Fast Freed Motorola Gates

Part(s) Speakers Speakers Speakers Tubes, Speakers, Radios, TVs

Capacitors Potentiometers, Resistors

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188

General Electric

Tubes, Capacitors, Speakers

194

General Radio

Transformers, Radios

199

Hallicrafters

Short Wave Equipment

201 210 213 214 216 218 220 222

Hammarlund Hytron/CBS Dearborn Wire IRC (International Resistance Co.) Jackson Jefferson Electric Jensen E F Johnson Kester Lenz Littlefuse Machlett Magnavox Mallory/North American Capacitor Thordarsen-Meissner Merit Coil & Transformer Micamold/ JW Dawis James Millen Muter National National Union Arvin Ohmite Dukane (Operadio) Packard Bell Philco Philmore Pilot Quam-Nichols Radio Condensor Company RCA Radio Craftsmen Emerson/Radio speakers Raytheon Rola Ross Telefunken?Philips?

J P Seeburg MASCO (Mark Simpson) Solar Speer Sprague Stackpole Standard Coil Stromberg-Carlson Superior Tube Co. Sylvania/Hygrade Triplett Tung Sol United Electronics

Short Wave Equipment

224 228 230 231 232 235 238 239 240 242 244 245 247 248 251 252 254 260 262 264 270 273 274 275 277 280 285 286 288 289 295 296 300 303 304 305 308 310 312 321 322 323

Tubes Wire Resistors, Potentiometers Tube Testers Transformers Speakers Sockets Solder Wire Fuses Tubes Speakers Capacitors, Resistors Transformers Transformers Capacitors /Speakers Capacitors, Connectors Resistors, Potentiometers Tubes, Speakers, Short Wave & Hi-Fi Equipment Tubes Radios, TVs Resistors, Potenetiometers Speakers, Amps Test Equipment, TVs, Radios, Computers Speakers, Radios, TVs Hardware, Fasteners Hi-Fi & PA Amps Speakers Capacitors Tubes, Speakers Hi-Fi Amps Speakers Tubes, Speakers Speakers Speakers tubes Jukeboxes PA Amps Capacitors, Speakers Resistors, Potentiometers Capacitors Potentiometers, Resistors Transformers Speakers, Amps Tubes Tubes, Speakers Test Equipment Tubes Tubes 12

328 334 336 337 338 343 345 352 366 371 381 383 391 394 396 409 412 416 418 423 433 437 438 439 440 446 449 452 461 465 466 472 489 503 508 516 524 532 547 549 550 551 554 555 569 572 575 579 589 590 606

Utah Wells-Gardner Western Electric Westinghouse Weston Zenith Astatic Essex New York Transformer Best Bournes Brimar?

Altec-Lansing Foster Transformer General Cement/Testors BIC General Transformer Heath United Transformer Corp (UTC) Philips/Norelco Cleveland Newcomb Gudeman Collins Cannon Good-All Wilder Empire Barker & Williamson Oxford Delco Pyramid Radio-Television Products Corp.

Caledonia Hickok United Condenser Triwec Transformer Ward Leonard Anaconda Midwest Standard Windings Corp.

ATR Amphenol Waldom Electronics Electrical Utilities Corp F & V Coil Windings Heppner Belden Bogen Shure Brothers Schumacher/Woodward

Speakers

Radios Tubes, Speakers, Wire Tubes Test Equipment Tubes, Speakers, Radios, TVs Phono Catridges Transformers Transformers Speakers Potentiometers Tubes Speakers, Transformers Transformers, Speakers Paint, Adhesives UK Import Components Transformers Speakers Transformers Tubes, Speakers Speakers Amps Capacitors Radios Connectors Capacitors Speakers Transformers, Coils, Phono Cartridges Capacitors Speakers Speakers Capacitors Transformers Transformers Tube Testers, Meters Capacitors Transformers Resistors, Potentiometers Wire Speakers, Transformers Transformers B+ Vibrators Sockets, Plugs, Connectors Speakers Capacitors Transformers Speakers Wire Speakers, Amps Microphones, Phono Cartridges Transformers, Chokes 13

607 614 616 621 631 637 648 649 658 682 699 705 706 708 710 713 719 720 722 732 733 738 742 748 749 757 756 767 771 772 773 776 781 787 789 793 794 795 809 816 828 830 831 840 842 843 845 847 851 871 878

Consolidated Simpson Illinois/Ampeg Amperex Pickering/Stanton Central Coil American Radionic Electro Voice (EV) Sangamo Electrical Windings Keystone Ajax Pioneer Bell Standard Condenser Cetron-Taylor Carbonneau Methode Milwaukee Resistor Radio Materials Corp. (RMC) Alpha Lewis & Kaufman Esquire Russell Speakers Co. Cetron-National Grand Transformers Universal Quincy Speaker Manufacturing Co. Penta Labs Muntz Forest Electric Ogden Coil & Transformer Vacuum Tube Products Sonatone McGregor McIntosh Harmon Kardon Atlas Varian Associates Dale Midland Triad Better Coil & Transformer Ampex Tetrad Klipsch International Rectifier University Drake Precision (Grommes) Acro Products (Acrosound)

Wire Meters, Test Equipment Capacitors Vacuum tubs Phono Cartridges Transformers Capacitors Speakers Capacitors Transformers Eyelets, Grommets, Hardware, etc.

Capacitors Speakers, Hi-Fi Equipment Amps Capacitors Tubes Speakers Connectors Resistors, Potentiometers Capacitors Wire Tubes Speakers Speakers Tubes Transformers Speakers Speakers Tubes TVs Transformers Transformers Tubes Speakers, Phono Cartridges Speakers Hi Fi Amps Speakers, Hi-Fi Amps Speakers Tubes Resistors, Potentiometers Speakers Transformers, Chokes Transformers Speakers Phono Cartridges Speakers Diodes, Transistors, Ics Speakers RF Equipment Hi-Fi & PA Amps Transformers 14

879 883 885 888 892 897 906 908 918 928 932 933 934 935 1005 1052 1056 1059 1098 1113 1149 1191 1279

Litton Mohawk Condensor Manufacturers Connector Corp.

American Transformer Tresco Coilcraft Aerocoil Oaktron?

Acme Coil & Transformer Atlas Magnetic Coil Manufacturing Oaktron?

Electrons Inc. Northlake Pacific-TMI Fisher Channel Pyle Acoustic Fiber Sound Curtis Mathes Micro Magnet Weber VST

Tubes Transformers Capacitors Connectors, Sockets Transformers Transformers Transformers Transformers Speakers Transformers Resistors, Potentiometers Transformers Speakers Tubes Transformers Transformers Speakers Speakers Speakers Speakers Speakers Speakers Speakers

EIA c ode s for US made e le c tro nic c o mpone nts These are codes often seen stamped on components found in US made vintage tube equipment.

This list is circa 1955, and some codes have been reassigned or added since that time.

Code formats were not completely standardized, but a little deciphering will generally yield the info of interest. Note that many makers also stamped OEM (Original Eqipment Manufacturer) part numbers above or below the EIA code, in some cases parts makers or the customer elected not to include the EIA codes, so not all parts have them.

They generally follow the following format: (example) 3 22 590 4 where 322 is the manufacturer code (in this case Tung s o l), 59 is the year (1959), and 04 is the week.

One alternate scheme is: 2 74 940 274 is the EIA code (RCA) 9 is the last digit of the year (in this case 1949). Usually single digit date codes are from the 1940’s, but have on occasion shown up in later decades, even up to the 1970’s. If one has a general idea of the age of the piece in question, usually the decade can be divined from that.

Another alternate is in the format following: 1 88 -5 69 32 188 is Ge ne ra l Ele c tric . 5 is the plant code (in this case, Owensboro, Kentucky). 69 32 is 1969, 32nd week.

And another is like this: 3 22 610 4 -1 322 is Tung s o l, 6104 is 1961, 4th week, 1 is the shift code (1 would probably be the day shift) After about 1960, many tube manufacturers went to encrypted alphabetical date codes., such as: KE 1 88 -5 The reason was purportedly to allow factories to track the dates of manufacture of defective tubes (especially important in the case of OEM customers that might send back entire batches of tubes), but avoid possible consumer complaints about ”stale” tubes. This sounds perhaps a little silly 15

since the shelf life of tubes is decades, at least (indefinite in practical terms), but some OEM’s might have beenn a bit irritated by occasional consumer complaints such as ”my 1961 model TV has 1959 model tubes in it!”

Tubes made for the US military, or certain OEMs (such as some test equipment manufacturers) that requested it, continued to carry numerical date codes.

In years past, EIA (Electronic Industries Association) also went by the name of RETMA, and the original acronym of RMA (Radio Manufacturer’s Association).

Ano the r c o de fo rm at: s c re e ne d on the g las s o f vac uum tube s 30

10 22

312 is Sylvania factory code year 1960 week 52

Philips E81CC *SQ* gold pin Import M2462-479 = Swedish Mil marked , in the bottom Df2 D9L1 Df2 =6201 D=Valvo ,9 =1959

Mo o re and uns ure de c o ding ?

Next is to try decode a GE JAN 6BQ7A with numbers: 77-48 77-30 3 3173 can it be philips1963 or 73 ?

Telefunken ECC83 2 0073 is probebly a philips 1960

Philips 12AT7WA made in france .7827 ?

Philips import E88CC marked on top 1 7K (philips 1967) RCA 6E5 1 9X 12672 70-48

(can be a philips 1969)

RCA 6080 metal (59-1960) Marked 6 0 EX0 (60 can be a another code for RCA or a another manufacture?)

Raytheon. By 1935, were ”private branding” many of the tubes with Philco, RCA, GE, Silvertone, Motorola, etc. No one tube company was able to tool up for all the tube types, as it was not economical..

16

17

18

19

20

21

22

23

24

De c iphe ring the Manufac ture r's Produc tion Co de The valve coding used by Philips and associated manufacturers seems mysterical, but the markings are basically rather simple to decode. Let's take an example of the typical, I believe later, 3+4-character code. This should work with the 3+3 and 2+3 codes, too.

IS = Manufacturing code. This is the Philips-group internal code for GZ37 . There can be several

internal codes for the same commercial code. These are different versions of the valve type.

1 =Revision number. This is the original version of this internal code type. 2, 3, etc. would be revised versions. (Ignore if not present.)

B=Factory code. B = Mullard, Blackburn Works (later possibly Simonstone Works), UK. N.B. If you think that your valve shows the digit 4, look again. It's more than likely the very similar-looking triangle = Philips, Heerlen, the Netherlands 2 = Date code. Last digit of the production year. In this case most likely 1962.

H= Date code. Month. August. (A = Jan, B = Feb, ...)

3 = Date code. Week. 3rd week of August. (Ignore if not present.)

25

Mullard EL34 produc tion c o de s This wa s a po s t on an am p BBS asking about Mullard EL34 production codes, what they mean,

and a response: I k n o w this has be e n d is cus s e d he re be fo re , b ut I'v e m is plac e d m y hard copy of h ow to de c ip he r this . I h ave s e v e ral NOS Mullard EL3 4's , dark c h oc . brown bas e s . Etc he d c o de s a re as follows : : x f2 : x f1 : x f1 : x f2 : x f2

B9H2 B1E2 B1F4 B0L2 B2D3

Xf is the c ode for EL34

xf1 c o ding indic ate s Mulla rds m ade in the Blac kburn Wo rks , in the U.K., fro m the late '5 0s to the e a rly '6 0s . x f2 indic ate s e ithe r the Bla c kburn Wo rks in the U.K., o r Eindho ve n, Ho lland tube fac to ry (a fte r Philips Ele c tro nic s boug ht Mullard in the '60s ) The diffe re nc e s in the 2 fac ilitie 's tube s are in the ba s e s -c o lo r and s iz e , and the g e tte rs . Bo th fac ilitie s m ade the s e tube s fo r o the r c o mpanie s (fo r re branding ) as we ll.

In the c as e o f the 1s t le tte r, ie 'B' fo r xf2 that's the fac to ry c o de , xf1=Bla c kburn, x f2 =Blac kburn -o rEindho v e n, Ho lla nd. The 9 wo uld be 1969 (in the xf2 c as e ). The 'H' is the date c o de m o nth Aug us t. (A = J an, B = Fe b,... H = Aug ), and the '2' is ano the r da te c ode , the we e k. in this c as e the 2nd we e k o f Aug us t.

In the 'x f1' c as e the 'B' is Bla c kburn, the '1' is 19 61, the 'E' is May, and '2' is the 2nd we e k o f Ma y. e tc fo r the o the r tube s ...

This is info rm atio n I'v e rc v 'd/le a rne d fro m Vac uum Tube Valle y m ag az ine , a nd als o from wo rking fo r Philips Ele c tro nic s - Ele c tro n Optic s Div is io n (bas e d in Eindhov e n, Ho lland) fro m 19 84 - 1998 . -Ro n

Month 1971 1972 1973 notes Jan. CE CF CH For following years advance the 2nd letter by one alphabetically. For instance, Jan. 1974 would be CI, Jan. 1975 = CJ, etc. Note certain letters are skipped, I don't yet know which ones, but notice that the letter 'G' is skipped both for year and month. 'D' is also skipped at least for the month. Presumably you can work this backwards too. In other words, Jan 1970 would be CC (or maybe CD). Also note: 'P' and 'Q' are skipped for the month (first letter.) Does this mean they're skipped for the year (2nd letter)? When I know more I'll post it.

For most of the 1960's they used the earlier year/week code. I'm not sure when the change-over to the two letter code occurred. You can get an idea by checking the date codes on our tube lists.

Feb. EE EF EH Mar. FE FF FH Apr. HE HF HH May IE IF IH Jun. JE JF JH Jul. KE KF KH Aug. LE LF LH Sep. ME MF MH Oct. NE NF NH Nov. RE RF RH Dec. SE SF SH

26

.

Amperex, Mullard, Philips, and Valvo Tube Codes The Bre nt Je s s e e Re c o rding & S upply, Inc http://www.audiotubes.com/ MostAmperex, Mullard, Philips and Valvo tubes are marked with a group of symbols which contain coded information relating to the type, place of manufacture or country of origin, and the date of manufacture.

Apart from the interest of knowing when and where a tube was made, the code group can still provide useful type identification when the commercial markings have become illegible.

There were two types of code formats that used the same tube type codes, which were in use from 1948 until these companies stopped the manufacture of standard receiving tubes. The code format changed about 1955 or 1956. There are some deviations to this rule, and in certain manufacturing plants not all of the code protocol was followed exactly, with every batch of tubes. Prior to 1955, Mullard used a purely numerical code for encoding the tube type, but then adopted the code change as listed here after that. Therefore, for tubes made after 1955 by all three of these large European manufacturers, the code is fairly uniform and straightforward to decipher using these code lists. Of course, as mentioned above, there are deviations in the code that vary from factory to factory and from year to year. This list is presented as found on original Philips documentation. Brent Jessee Recording makes no claims as to accuracy, and presents this information for your use "as is" and "as found".

THE ELEMENTS OF THE TUBE CODE: The digits are often found near the bottom of the glass on the side of the tube. They consist of two or three lines of numbers, letters, and sometimes symbols. They will nearly all use the following convention, from left to right, top to bottom of the code group:

TUBE TYPE: This may be one, two, or three alphanumerics or symbols. For example, the code GA means the tube is a type ECC88, which is also a 6DJ8. These codes will be listed later in this webpage.

Pretty straightforwa rd, huh? Take notes, it gets stranger from this point on......

CHANGE CODE: What?? Well you might ask. This code appears to be for internal factory use, perhaps to trace various batches of tubes. Like the month code we will see later, we get a wacky sequence of symbols that recycled every three years. They allowed for 15 different batches, and in the years 1948-1950, a batch number 20. This cryptic code was used until 1956. This can be seen on the following table: Actually, coupled with the unique month codes, you could use the change code to zero in on the year and month of manufacture. Prior to 1956, anyway. For example, a month code of A and a change code of A would be unique to Jan. 1951.

27

After 1956, the code just became the following numbers and letters that would repeat as required: 0123456789ABCDEFHKLMNPRSTUVWXYZdfmrt Therefore, batch 0 was 0, batch 1 was 1, batch 10 was A, and so forth until the end of the list. This new code allowed for 35 tube batches after which, it must have repeated from the start again. The year and month started to be used at this point after 1956, so the change code is not really necessary in newer tubes to pinpoint a manufacture date. The purpose of these codes, indeed all of the change code, is unclear from original Dutch Philips documentation. The theory that they pertain to individual batches of tubes or "production runs" seems to be the most plausible, and is the purpose I have accepted as to their

meaning.

FACTORY: The factory o r country of origin. One symbol only.

YEAR: The last digit of the year of manufacture. This is only present in the code used after 1955.

MONTH: The month of manufacture. This gets a little screwy, as before 1955 there was a sequence of 36 symbols used which repeated every three years according to the following table:

In the code used after 1955, each month is re presented by a single letter in the sequence shown on the next chart. Re membe r, the last digit of the year began to be used with this code, and this will help identify post 1955 tubes.

WEEK: This is the actual week of manufacture within the listed month. Obviously goes as 1=first week, 2= second week, etc. Some documents and other sources I have researched indicate this week code was only added from 1961 onwards. It also does not mean that all tubes made since 1961 have the week code. Use the charts below to see if the week codes even apply to your tube.....

HOW THE CODES APPEAR ON THE TUBE: This can get pretty screwy, too. For the most part, on tubes commonly found in circ ulation today, the code is located on the side of the glass in dark grey paint, down low just above the bottom. It follows this convention before 1956: TTC

FM Whe re TT stands for the one, two, or three symbol tube type code, C is the change code, F is the factory and/o r country code, and M is the month of manufacture. On the bottom of octal base tubes the code is usually FM/TTC. After 1956, the code changed to the following several formats, with the manufacture year (Y) kicking in to the mix: TTC

FYM Another variation with the addition of the week of manufacture: TTC

FYMW 28

Another variation with a triple tube type number and the week: TTTC

FYMW And to completely confuse you, yet another triple type numbe r variation without the week: TTTC

FYM The best way to become familiar with these variations on a theme is to get some v intage tubes and practice. For the most part, tubes made after 1956 are what is commonly found on the vintage market today. This will re duce the number of code choices you have, and the tube type codes of the tubes you use the most will become committed to memory, as they never change.

In the early 1960's STC spun off Brimar to "Thorn-AEI Radio Valves and Tubes LTD" The history gets a bit complex.

This company made tubes under the Mazda and Brimar names, as well as Ediswan. FYI, Mazda was a British company for those who don't know, and in the 1920's Ediswan and Mazda were major makers of radio tubes.

Ediswan being the world's first radio tube maker (A joint efort started in 1883 by Edison Eletric Light Co and Swan Electric Lighting Co.) Many of Mazda's later tubes were made in French factories and are excellent. I have some of the 6V6GT's someone mentioned, and they are very nice sounding, and extremely durable. They are early production made for the war dept labeled "services plublic guerre". Guerre meaning war in French.

In fact one of the earliest 12ax7's I've ever seen was a Mazda made in France. It has the exact same plate as the first Amperex 12ax7. This Amperex tube is very rare and may not have even been made in Holland, though the label says it was. The getter ring of the Mazda is unmistakably Telefunken. It's very nice.

29

THE FACTORY AND COUNTRY CODES: Often quoted by tube expe rts, and just as often misread and/or misinterpreted by the same experts. The list reproduced here is about the most comprehensive I have seen after researching original Philips documents (poor quality scans of these are available on various websites on the Inte rnet) and several other partial sources. I have scanned a printed list of the most comprehensive factory/country codes, as they contain a great many symbols not found on the standard USA compute r keyboard. Remember, this code element follows the tube type code and the change code, which a re always the first two codes in the code sequence.

30

TUBE TYPE CODES: This is a huge list. This code is really only necessary if the factory label becomes rubbed off of the tube, so you can tell what tube you have. Otherwise, it just confirms what the label says.

Most audiophiles are concerned with date codes and, to a lesser extent, the factory code. This is for reasons of finding tubes that could be put together in matched pairs. It is more likely that tubes from the same date code and factory will match up better than tubes from different batches and factories. But it is nice to have these codes available if you are not sure what type of tube you have.

31

PHILIPS CODES This happened world wide, I have recently found that links to a listing of source codes that Philips used to indicate where tubes sold under the various Philips brands were actually made. Philips sold tubes in various countries under the Philips, Miniwatt, Rogers, Amperex, Mullard and Valvo names. The codes did not indicate that Philips sold any given quantity of tubes from any of these factories, just that they purchased and resold some tubes from each at various times.

Philips Source codes exist for: • Amperex USA • Bharat Electronics (Private) Ltd. India • Chinema Television • CIFTE France • Electronic Tubes Ltd. UK • Elektrinski Indusrija Yogoslawia • EMI UK • English Electric Valve UK

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Ferranti UK Fivre Italy Hanadon Works Australia Hitachi Japan Hyperlec Brive Spain IBRAPE Brasil IPERPESA Peru Lampra "Z" Spain Loewe Opta Germany Marconi Chelmsford Marconi Osram Valve UK Matsushita Electric Japan (2 Locations) MBLE (Mazda) Belgium Mullard: 8 UK Factories Papesa, Argentina Philips Copenhagen Philips Chile Philips Monaco Philips Electric Lamp Philippines TIC Philips Export Corp USA Philips Holland and UK (12 Factories) Rogers (Philips Electronics Industries Ltd.) Canada Radiotechnique France (3 plants) Siemens & Halske Germany Standard Telegraph and Cables UK Telefunken Germany Thorn AEI UK Toshiba Japan Tungsram UK Valvo Hamberg Germany Venolande Venezuela Visseaux France Wiener Radio Werke WIRAG Austria

32

I n t r o d u c t io n Most Philips valves are marked with a group of symbols which contain coded information relating to the type, place of manufacture or country of origin in the case of bought in valves, and the date of manufacture. Apart from the interest of knowing when and where a valve was made, the code group can still provide useful type identification when the commercial markings have become illegible.

This document details two code formats using the same type identifiers which were in use from 1948 to the end of manufacture of receiving valves. The code format changed from the 'old' to the 'new1 system around 1955/6. From examination of actual valves it is clear that whatever may have been the decree from Eindhoven, there were apparent deviations on the ground at manufacturing plants in other locations. Again based on examination it seems that prior to the coding system described herein, a purely numerical system was in use for encoding the type and that for its own production, Mullard continued to use this until adopting the 'new' code in 1955.

Some of the information herein is open to interpretation, translation from fairly terse Dutch original documents or based on examination of actual valves. No claims of absolute accuracy are made.

2. T he code The code has the following elements, represented in the generic layout guide by the bold letters: T

Type. May consist of one, two or three symbols.

F

Manufacturer or country of origin. One symbol.

Y

The least significant digit of the year of manufacture. This is only present in the 'new' code.

M

Month of manufacture. In the 'old' code this was represented by a sequence of 36 symbols which repeated every three years according to the following table: Month

1948 1951 1954

Jan Feb Mar

1949 1952 1955

R S T U W X Y Z d k m r

A

B C D E F H K L M N P

Apr May Jun Jly Aug Sep Oct Nov Dec

1950 1953 1956

t 0 1 2 3 4 5 6 7 8 9 +

In the 'new' code each month is represented by a simple sequential letter.

Jan Feb Mar

Apr W

A

B C D

May E Jun F Jly G Aug H

Sep Oct Nov Dec

I J K L

Week of manufacture within month. 1 first, 2 second etc. This seems to have only been added

33

from 1961 onwards although that does not mean that all valves made from 1961 bear it. A valve from Whyteleafe has been noted to have what looks like open week of year coding: S027.

C

Change symbol. The intention of this is not clear but it may have been a symbol that was to be

changed for each batch produced. In the 'old' code there was no year but the change symbol sequence was replaced in three year cycles such that this, taken together with the month symbol, would be a unique combination for any particular year. For example: Month W with change T would be unique to May 1955. The change sequence was as follows:

In the 'new1 code this was just a sequence of symbols which appear to have no purpose other than perhaps provide batch traceability. Evidence indicates that this aspect of the code may not have been applied too rigorously at some locations. It is found to be missing on examined valves of Australian Philips manufacture for example. It was not applied to bought in valves. The sequence to be applied was: 0123456789 ABCDEFHKLMNP RSTUVWXYZdfmrt Presumably this sequence was then repeated if necessary. General observations: In the type code list there are several examples of valves having two or more codes. This is generally due to differences in construction but there were errors of multiple allocation. There are also instances of two valves sharing one code. These may have been errors but the bulk of the listing here is taken from original documents "Codes for Receiving and SQ Tubes'. One or more other list(s) existed and some codes were probably used again for other devices like CRTs or geiger-muller tubes for which there would be little likelihood of mistaken identity.

In the list herein most types under one code are equivalents but where they are not, the word 'also' has been inserted to clarify the point. A few valves having very similar characteristics do sometimes have the same code, at least until another is allocated e.g. DY86 and DY87.

Suffixes are used to denote some characteristic of construction where this is shown in original documents, as follows: bant Bee

dev en min

new old

"Bantam" or "bantal".

The significance of this is not mentioned in original documents.

Development or provisional number 'mit Einschmeltz-emaille' Miniature.

New or revised construction.

Old construction

34

C o d e a p p lic a tio n

'OLD CODE

Examples of deviations

Examples of "correct" code format

Brasil F YM TT C

TTC FYM

Australia

TTC FYM W

TT F YM

TTTC FYM W

Eindhoven TTC W F YM

TTTC FYM

'NEW CODE

35

S i n g l e s y m b o l ty p e c o d e s Thes e codes were app lied to B7G typ es only.

36

T w o s y m b o l ty p e c o d e s AC AD AE AF AG AH Al AJ

AL AM AN AS

AW43-89 EC88 EL500 6GB5 6EU7 CV4035 PY33 DL97

ECC230 6080 AX50

LC97 3FY5

AU

LF183 YF183 4EH7 LF184 YF184

AW AX

Ad Af

A0 A2 A3 A4 A5 A6 A7 A8 A9

4EJ7 6GK5 6GK6 85A1 CV4011 M8196

347 2C1000 E88C 8255

EC800 XL500

BU BW BX BY

BZ Bf

B1 B2 B3 B4 B5 B6 B7 B8 B9 B+ CA CB CC CD CE CF CG CH Cl

EC1000 PCF802

9JW8 6CQ8

CJ

PY83

CK

BA BB BC BD

XCF86 6DK6

BE

12DT8

BG

E80CF 7643 7475 PEN4DD CV4029

BH Bl BJ

BR BS BT

PC97

4FY5 PL1607 YC97

AT

BP

E86C

ECH800

CL CM CN CP CR CS CT CU

BN

Cm

Cr Ct

5639

2GK5 M2EL

38EL XL84 XCC189 XL36 MX153 YL1000 M1DL CV4049

M7EF 95400 4-OA31 M9ECC.1 M13PCC VX8250 3GK5 35C3

C0 C2 C3 C4

C9 C+

EC900 PCF801

8GJ7 XCF802 LCF802 YCF802

6LX8 DB DC

DH Dl

PL84 min 15CW5

DJ

also

DL DM

VX8252 LCF86 YCF86 5HG8 3BA6

6BZ6 6DE6 12AL5 EL36 6CM5 PCC88

7DJ8

ED

DP DR DS DT DU DV DZ

EE EF EH El EJ

3A4 DL94 3V4 CV2983 also MX164 DW2 1561 1805

VP4B VX8179

EK

EB41

EL EM EN EP ER

EC37

ES ET EU EV EW EX EY

EZ Ed

ECC31 ECC32

EF37A EF91

6AM6 1883 EL35 EZ35

OA3 CV3798 FW4-500 PM24M

PF183 4614 SP13

VX8194

Ek

6GJ7

Em

SP13C AZ11

PC900

Er Et E0 E1 E2 E3 E4 E5 E6 E8 E9 E+

4HA5 QV10-P8 7453 3BE6

3DE6 75C1

EN33

6ER5

Df

also

Dk

PF86

MX155

Dm

Cd

6463

Cf

VX8205 EC86

Dr Dt D2

402 3AL5 3CB6 3BZ6

Ck

EC

Ef

PCF84

CV5304

5Y3G 80 en 80dev DL93

PY300 ECF801

also PB-1 6201

CW CZ

EA EB

6686 V1ELL

ECC808

OKL1B(p)

6-OA31 8-OA31 PCC34 18045 EC95

E81L

C6 C7 C8

DF

PEN40DD CZ30

LL500 18GB5

ELL80

3CS6

12C5 PCF806

D+

18046

E288CC 8223

DD DE

MX154 VX8189 6AQ5A 12AU6A

62BTA

C5

12CU5 6CU5 4GK5 CV1377

ECF802 6JW8

ECC186 7316 also ECC282

M2PE

M3DV M4PCF

ECC88 Bee E184CC

Dd

5902 M8200

also YL1000 E55L (M5EL)

E55L (M6EL)

8233

FA FB FC FD

1A7GT FC13

4633 DAC32 4618 UY21

4654 AL1 5Z4 6A8G

6J7 4673 4682 4683 DL35 1C5GT 4688 C tech

37

FE FF

4689P C tech 6A8

FG

VX8114

FH Fl FJ

6K7 60EH5 HCH80 4699.5 etc 6J8G

FK

FL FM FN FP FR FS FT FU FV FW FX FY FZ Fd Ff

Fk Fm Fr

Ft F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F+

GP GR GS GT GU GV

CV140+ CV417+ CV465+ CV466+ CV467+

GW

6F6G

GY

6F6

GZ

CV468+ CV469+ CV858+ CV2129+

6V6G

Gf

ECC82

GX

6V6GT 12SK7 12SQ7 18040

PL3C23 25Z5

25Z6 AB2 (V base) ABC1 dev ABL1 dev

7AU7 EA70 AD1 AF2 AF3 AF7 43 AK2 dev 35L6GT AL2 AL4

Gk Gm Gr G0 G1 G2 G3 G4 G5

GF GG GH Gl GJ GK

ECC88 UM84 VX8167

QV9-P10 EH90 6CS6 CV131+ VX8116

CV133+ PC95 4ER5 EL81F CV136+

GM GN

CV136+ loose cathode EM81 6DA5 CV138+

EA52 EA52 6923

1EA EN93 6D4

G+

V2ECC

HA HB HC HD HE HF HG HH HI HK

AZ41 95104

6CQ6 EL38

Hr Ht H0 H2 H3 H4 H5 H6 H7 H8 H9 H+

DF21 DF22 5ECC dev DF70 CF50 DK21

IA IB 1C ID

ORP20PW ORP20

IE

CBL1 dev XC95 EF97 CBL31 ECH41 UM5 UL43 UCH41

HW

CY2 dev

also EL521 CY31 60FX5

CK1 (M) ECL80 6AB8

EL44 DK40 DL21

Z701U DL40 DL41

ECF83 E182CC

7119 4152-02

IF

PC93 also 5876

IG

6205 CV2432

IH II IJ

185BT

IK

PZ36

IL IM IN IP IR IS

6286 27SU

IT IU IV IW IX IY IZ

Im

PF83 also MX132

Ir It I0 I1 I2 i3 I4

EC158

ORP90

PCC189 TY86F GZ37 CV378 6BJ6 VX8227

I7 I8 I9 I+

XCF80

JA JB

HCC85

95398

Ik

EC 157

XCH81

XF80 7025

EF184

6EJ6 JC JD JE JF JG JH JP JU

ORP31

PL500 27GB5 PC88 4DL4 CBL6 EA50 2B35 ECF1

JZ Jd

EL30 LCF80 YCF80 6LN8 TH2 UCC83

Jf

ECF806

JO J7

MX150 4069 ME1404

J8 J9 J+

3DT6 V3ECH LCL84 YCL84 10DX8

also MX1 08/01 KA KB

ORP30 EC156

PC92 EF183 EY180 ECC83 12AX7

E181CC ECC189

Id If

ORP10 6EH7

E180CC 7062

PM84 EF6N also

PY180 ORP11 6211

I5 I6

EL360 VX8240

was used for Hamburg PM84 till 3.8.58

VX8141

CL4 GZ40 old CL33 CY1 CBC1 dev

Hd

Hm

41 DK33

HL HM HN HP HR HS HT HU HV

HX HY HZ

Hk

E83CC 6681 EF92

DF33

AZ12 AZ31

6ES6

tight cathode

GL

VX8140 EC52 EBL31 PCF82 EC57 EBF89

G6

DF91

1T4 50L6GT AZ1 78 AZ4

12AU7 UCH5

6DC8

HJ

GA GB GC GD GE

4641

Hf

KC KD KE KE2

DL71 DLL21 also DLL31 DF35

E1C EL34 old EL34 new

38

KF KH Kl

DC89 E424N A4110 M8144 CV4033

LP LR LS LT

KJ

EF98

KK

6ET 6 DAC21 E443H

LU LV

E447

I_X

KL KM KN KP KS KT KU KV KW

KX KY KZ Kd Kf

Kk Km Kt K0 K1 K2 K3 K4 K5 K6 K7 K8 K9 K+ LA LB LC LD LE LF LG LH LI

EC81 EA40 EA51 EAF41 EB34 CBC 1 (M) EB40 EY51

6X2 EBC3 EBC33 EM1 PL83 Bee EM4 EM34 6C D7 EQ80 6BE7

EBF2 PCC809 EZ41 EBF11 EBF32 EBF35 EBL1

LW

DA90

MV

TDD13

1A3

MW

EL6

EC H35 Mull

MX MY MZ Md

EL11 EL12 EL20 EL81 6CJ6 PCF82

ECH41 EC H80 6AN7 ECL11 TDD4 DC79

EC40 EC41 DK32 1A7GT EC81

6R4 ECC40 UY11 EC H3 EC H4 VX8206

4671 UBF89

19FL8 LK

EFF51

LL LM LN

ECH11 ECH21 ECH33

also MX145

EF93 6BA6

LY

EE1

LZ Ld

EF6

Mk Mm

PL38 GZ30 new GZ40?

Mr Mt M0 M1 M2

KB2

EEP1

Lf

EW 60 ECL83

Lk Lm

EZ2 EL91 6AM5

Lr Lt

EZ4 EF80

M3 M4

6BX6

L0 L1 L2 L3 L4 L5 L6 L7 L8 L9

EF8 EF9 E1F

EF12 EF22 EF36 EF39 EF40

L+

also CV2031 EF41

DF65 EF11

6CJ5

EBL21 EBFS40

Mf

MA MB MC MD ME MF MG MH Ml MJ MK

ML MM MN MP MR MS MT MU

EF42 EF50 EF51 EF100 DL65 EFM1 VX8207 EFM11 EL86 6C W 5 EBF83 6DR 5 DL21S EFP20 EFP60

EK2 EK32

EL2 EL3N EBF80 en UB41

M5 M6 M7 M8 M9 M+ NA NB NC ND NE NF NG NH NJ

KBC1

EL32 EL33 EBC80 6BD7 EL39 EL41 6C K5 EL42 95105 EL42

NL NM NN NP NR

EL51 EL60 EL80 en PL83 en

KF3 KK2 KL4 AZ50 UAF41 5651 UAF42 12S7 EC H83 6DS8 MX156 UL41 45A5 UBF11

UBL1 UCH41 UBL21 UCH4 also

D3a NS NT NU

UCH11 UCH21 UC H42

NV

TDD13C UAF100

14K7 NW

Nk Nm

UC H100 UCL11

UF9 UF9 UF11?

PY80 min UF41

12AC5 Nr Nt N0 N1 N2 N3 N4 N5 N6 N7 N8 N9 N+

VCL11 CF2 VY2

PA

DL92

UF100

UY2 UL100 UM4 UY1N UF21 EL41 en UY41 UY100 UY42

3S4 PB

ELS

also NK

NX NY NZ Nd

PC PD PE

DL72 als o MX165 ECH42 6C U7 EL61 PY80

19X3 PF PG PH PK

PL PM PN PP PR PS PT PU PV

UF10 6007

Aa Ba Bas

Ca Cas Oa Ce Ed E2c E2d EY88 6AL3

PW

PX PY PZ Pd

Pk Pm Pr Pt P0 P1 P2

C3b C3e 5Y3GT E452T EL6/400V EL12/325V EL12/375V EM4/100V UM4/165V UM4/200V UL44 EL43

39

P3

EBC41 6CV7

P4 P5 P6 P7 P8 P9 P+

4689K EL43

RA RB RC RD RE RF

AF2 AL5 ELS

RG RH Rl RK

RL RM

UL44en 4654K UBL3 UCH5 ABC1

VCL11 VY2 X13

also MX151 M1EL EL131 UF42 E130L 7534 UBC41 14L7 C443 DAF91

RS RT RU RV RW

RX RY RZ Rd Rf

Rk

Rm Rr R0 R1 R2

R3

SJ SK

SL

UL2

DAF40 EL45 AZ41 Bee 5V4G ECH42 Bee EL95 6DL5 CV4109 DAF41 with add F DAF40 EL41 Bee

6J6

Sf

CCH35 EC91 6AQ4 EF54 EF55 VX8196C

Sk

UF6

Sm

EC55 TD03-10 DCC90

6AS6W EL22 EZ22 FW4-800 CY32 DL33 3Q5GT EAC91 M8097 CV4059 EB91

SM

SN SP SR SS ST SU SV SW

SX

SZ Sd

Sr

3A5 S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S+

TA TB TC TD TE TG TH

EC80 en EZ80

SY

DK91 1R5

RR

SA SB SC SD SE SF SG SH SI

EAF42 6CT7 EAF80 EL21 ECC35 EF55 ECC91

DF92 1L4

RP

R8 R9 R+

EC53 DL70 EL37 GZ32 5AQ4 EL44 E446 (O) CV273

UY4 EBC41 Bee DC80 6DC EZ40 old 4060 EF41 Bee UBF80 en 18300 18042 en PL81 21A6 EL34 6CA7 EF80 UCC40 Z502S

1S5 RN

R4 R5 R6 R7

EL81

TJ TK

TM TP TR TS TT TU TV TY TZ

506

EY50 4684 4688

UM

1832 UBC41 Bee

UN

UF5

DF96 1AJ4 XCF801 DAF96 1AH5 also MX142 LCF801 5GJ7 UCH42 Bee UY42 Bee UAF42 Bee UCH81 19D8 ECH34

UP UR US UT UU UV UW

UX UZ

Ud Uf

Uk Urn

AY1

EL50

Ur

AZ2

T2 T3 T4 T5 T7 T8 T9 T+

Z805U UF41 Bee EY80 min XF85 ECC81 XL86 TD03-10B EL82 6DY5 3AT6 PL82 16A5 KK32 Mull DF74 EL83 en MX161 DF67 DL67 E83F en UCH81 min

UA UB UD UE

UL41 Bee L413S A4110 DL96

VD

3C4

VF VG

Td Tf Tk Tm Tr Tt T0 T1

CF7

EAF801 L416D

UY3

UF UG UH Ul

CF3 Cf

UJ

Bh

UK

UL

DL67/5 6J5G EF43 5718 CV3930 also EL802 37EL UF43 3AV6

Ut U0 U1 U2 U3 U4 U5 U6 U7 U8 U9 U+ VA VB VC

VE

VH VI VJ VK

VL VM

6BQ6GBT 6CU6 LC900 3HA5 EF81 ECH4G DL67/65 UQ80 EAF42 Bee AZ32 12SK7GT DK96 1AB6 E447 (E) 12SQ7GT QQE03/12Bee 12SA7GT E90CC 5920 CV5214 LC95 YC95 3ER5 QQE02/5 Bee DY30 1B3GT XC900 AC2

EL520 DF67/5 E446 (E) 6SA7GT 6SK7GT 6SQ7GT 35Z5GT UY41 Bee 18042 6086 E80CC 6085 E80F 6084 E80L 6227 E83F 6689 ECC81 E81CC 6201 EC92 new UC92 new ECC89 6FC7 5842 41 7A E94CC ORP92

40

VN VP VR

PC96

Wr

95124

Wt

E188CC 7308

VS

EM84

VT

6GF6 XCC82 7AU7

VU

PCF86

W

PL136 35FV5 EL183 PCL85

VW VX

18GV8 VY VZ

vt WA WB WC

WD

Valvo PCL805 UY89 6AN7A MX149 PM22A 6BD7 min 6BH5 min 6M5 min

W0 W1

XC XD XE XF

XG XH

XJ

WF

ORP50

XK

WG WH

M3EFP 9U8

E1T WL WM WN WP WR WS

CV4084 E80F Bee

UM34 ECL86 6GW8 also CV4011

WU WV

C3JA DW4-350

WW WX WY WZ Wd

18042 Bee

XL

PCF201

XN XR XT XV XW XX Xf Xr

Xt X0 X1 X2 X3

UM34/165V

X+

EF94

Wk Wm

CV4098 PY82 19Y3

YZ

E282F

Y0

EL300 PL300 6CY5 EL502 E9Z dev EL504 6GB5A

6AU6 E83F Bee

YY

Ym Yr

5672

18045

Wf

YT YU W YW YX

E235L DW4-350 DW4-500 E236L

ECC186 (L) DL620

YC

DM70 1M3 also DM71

6X9 ECL80 en

ZH

ECL85 6GV8

DF60 5678

Zl

EF71 rel

PY80 en PY82 ECH200

6V9

Yd

7320 PL2D21 XF184 XF183

HL90 12AQ5

ZJ ZL

95106 PY800A

EL34 E84L

PL81B

ZG

ZK

YS

5644 PCF200

ZF

EF80 en ECF200

PL81 en PL82 en

YP

E80T 6218

ECC81

CV4086

5899

ZE

YK YL YM YN YR

PCH200 9V9

6AJ8 EC56

CV1868

16AQ3 CV468 Ultra M6EF 12DJ8 GZ41

ECH81

YJ

8U9

X4 X5 X6 X7 X9

ELS

18046 Bee

PFL200

YH Yl

8X9

25L6GT E80L Bee

E182F

YG

CV477

also

also

PCL86 14GW8 XR1-1600A

401 XY88

PY32 bant

WK

YE YF

EBF81

XA XB

WE

5840 EF730 5636 E80CC Bee

1AC6

ECC2000 VX8195C

XI

Wl WJ

YD

W2 W5 W6 W7 W8 W9

also EF800

EL803S

EBF81 min DK92

E186F 7737

XCL84

ZM ZN

ZP ZS ZX

18501 18502 also

MX130 EZ90 6X4 EBC90 6AT6 EK90 6BE6 DL22N

6AD6 6BL6 6J8 12BL6 12J8 5854

LFL200 11Y9

ZV ZY

18500

DY87

CV3986 6021

ZZ Zd Zf

Zk Zm Zr

VX8222C LY88 20AQ3 4068 5719 EF40 Bee 5749 6BA6W 6005 6AQ5W

6080WA

Zt

ECF201

Z2

6U9 LCF200 5X9

Z3

LCF201

Z4 Z5 Z6

Y2 Y3

E81LBee EC97 6FY5 PY81 17Z3 EC81 EF85

7.7 28

ZP1080

Z9 Z+

4067

Y4.0

6BY7 EABC80 min

dA dB dC dD

6112 7895

dE

6CG7 LCH200 5V9

Yt

Y4.1

Y5 Y6 Y7 Y8 Y9

EABC80 en VY1

6BU8 EFL200 6Y9 ECH81 en

EC80 6Q4

Y+

PL57

ZA

6DT6 12FK6

ZC

UL41 Bee Ag plated pins 12AD6

ZD

XCF201 PY801 ZP1081 6111

PL6574 DY86 1S2 DY87 1S2A

dF

ZB

5U9 XCF200

dG dH dl

12X4

LL86 10CW5 5949

41

dJ

PCL84

dK dL

15DQ8 LL521 GY501

fj fK

3BH2

dM dN

V2VY XL521

LCL85 10GV8

dP dR dS dT dU dV

CV287 YL1220 6AU6WB EN91

PL435 LCC189 5ES8 also

dW dX dY dZ dd

PL5822Du PL522 EF5000

CV4108 V6ECC PD500

9ED4 df

PY500

dk

42EC4 PL505 40GK6

dm dr dt d0 d1 d2

V7PCL CV2901

d3

E810F 7788

d4 d5 d6 d7 d8 d9

fL

LCL86 MSEC EA53

EL136 6FV5

fM fN fP fR

kl

ECL82 Bee

kJ

also EF802 EL83 Bee also ECC801S PL84 Bee UCL82 Bee UF86 QQE02/5 Bee

QQV02-6

fS fT fU fV fW fX fY fZ fd ff fk fm fr ft f0 f1 f2 f3 f4 f5

N22PL N22XL M6ECC LSD2

Z303C E35CC EM84 EC71 EF732 CV2281 EF731 5609

5U8 12BY7A LY81 11R3

5609V VX8234 GZ34 bant CV1377 ECL84 6DX8

M13PL M6DY GY86

f7

6972 M7EC EC98 EY500

PY81 en

f8

6EC4 24DF

UABC80 en UCH81 en

f9

to

also

d+

N22LL 19KF6

EL803 UF80 en

f+

ECC83 low microphony also

CV4110 M10PL

also

YL1080

kA

YL1081

fA fB fC fD fE fG

UV4-250

LB4-2

KB kC

MX1 24/01

MX133 EL505 6GK6 TD1-100A

kD

UF85 also CV41 1 1

6V4 EZ40 6BT4 CV3891

kE kG

also 18504

kK kM kN kP kR kU kV kW kZ kd

km kr

kt k0

GZ40 UM81

EL84 Bee DY51 1BG2

E3LL dev ECF86 6HG8 HN309 EY87

1S4 5R4GYS ECH84

6GX8 XCL86 DF61N M4ECC XF86

mA mC mD mE

TS65 D12L D20F

XCL85

PY800

PABC80 en ECC83 6AM6S CV302 not

m5 m6 m7 m8 m9 m+ rA rB rC rD rE rF rG rH

CV303 not UCL83

mJ

EF89 Bee also

mK mN mP mR mS mT

12AU7S CV4039 M8096 YL1130 AB2 (O) GZ34 UF85 min UCH81 en EF80 Bee

UABC80 en

G5S6 UF80

UF85 EF85 en E280F EZ40 Bee new EZ80 Bee PY80 EY80 PY82 Bee

EABC80 6AK8 E283CC ECH81 Bee

UCH81 Bee EC8010 ECC84

ECC809 EF804S 95107

DC80 PABC80 9AK8 UABC80 EF805S K81A QQE03/12Bee

QQV03-10 ME1403

rJ rN

UF89 Bee DY86 DY87 GZ33 CV378 GZ34 made in Eindhoven

rS

finished

mG mH ml

E82CC

rl

finished

mF

PL83 15A6 also

6U3 m3 m4

ECC82

XC97 CV4517

EL83

6CK6 CV1672

CV359

mX mY md mk mm mr mt m0 ml m2

EAM86

also N7ELL

k1 k3 k4 k5 k6 k7 k8 k9

mV mW

EL84

6JX8

kk

mU

4662 6BQ5

EZ80 en new EZ80

EM87 6HU6 MX147

rW

E180F 6688 HF93 12BA6 E181CCBee EL85

rX rY rZ rd rk

6BN5 EL84 min 4699N 6BK4 EM85 XL505

rT

rU rV

42

rm rr

rt r0 r1 r2 r3 r4 r5 r7 r8 r9 r+ tA tB tC tD

LL505 CV2031 PCC84

7AN7 4646 DF64

DL64 1AX2 581 4A

12AT7WB PCF80

9A8 EM80 6BR5 6SN7GT ED500 N23PL

EL503 UY85 EY86 6S2

t2 t3 t4 t5 t6 t7 t8 t9 t+ 0B 0C 0D 0E 0F

0H

6S2A

tH tl tJ

EF86 Bee E99F 7694 25Y5 (J base)

VX8163 PL82 Bee

tL

4694 M5DY

tM

DY802 PC86

IK

IN IP tR

tU tV tW

tX tY

tz td tf

tk tm tr tt t1

0S 0U 0W

0d 0f

EF89

M11EL EL5070 ECC85 GZ34 4373 18046 en EBC81 Bee PCC85 9AQ8

6A8GT LA4-2 VX8168 75 CV614 EF804 EL81 Bee PL81 Bee PL508

ECC180 6BQ7A PL57K YL1080 ECL82 6BM8 EBC81 EY70 rel

12SA7GT 18015

03 04 05 06 07 08 09

1J 1V 1W 1Y If

1k 1m 1r 1t 10 11 12 13 14 15 16 17

KT66 12SK7GT 12SQ7GT EC83.1

18 19 1+

LL504 DM160 2A

UM80 19BR5

0m 0r 0t 00 02

1G

PCC89 7EF7

6977

0k

1E 1F

CV4005 12SN7GT

UCC85

tT

PL5822

25Z6GT

ECC86

PCL81

LY500

0L 0M 0N 0P

0Z

tS

EL508 6KW6 6BK4A Z500T Z501T

0K

4CM4

6DA6

V10PL UL84

6BD7A 01 0J

1C 1D

V7PL PL802

YL1081

0G

EY87

tE tF

PL504 N22EL

UF89 XL504 N55RPY 18016 EY81

6R3 6SA7GT 6SK7GT 6SQ7GT N54RPY

UY85 Bee PL95

0+

E95F 5654 6AK5W UBC81

1B

03DF

04DL dev CV4011 also

2S 2T 2U

03DF dev

2V

DF62

2W

DAF92 1U5 CV3912 UCL82

2Y

2f

DF66 DF72 DL66 DL68

2k 2m 2r 2t 23 24 25 27 28 29 2+

DL95 3Q4 DL73 DL75 DL98 3B4 DY80

3B 3E 3F 3G 3H 31 3J

DY70?

EA76 6489 EC70

3K

EC90 6C4 EF70 EF71 EF72 EF73 EF95

ME1402

4066

CV4009 PL81F DL69 AN1

CV467 2B 2C 2D 2E

2Z

2d

6CH6 CV2507 DC70

ME1401

4065

50BM8

EBF82 EL821

LSD5 LSD7 LSD8 XCL82 LSD24

3L

GY802 EL86 Bee PCF810

3A3 PL521

5837A MX108 MX118 MX119 11AF9

PCL83 XY500 XL508 TD03-5 Z300T Z800U E82M

Z801U UF81

CV4019 Z900T E91H 6687

3M 3N 3P 3V 3D

6CB6 EL90 6AQ5 85A2

Z70U EBC91

6AV6 3X

6AK5 EL70

3Z

150C2 HBC90 12AT6 HF94

EY802

3d

HBC91

also

3f

3k

21 2J

PL6574 UBC80 CV4012

12AV6 PCL82 Bee HK90

2K

5643

2F 2G 2H

3Y

12AU6

EN32

12BE6

3m 3r

EN70 2L 2M 2N 2P 2R

EY70 EY91 DAF70

LSD3 LSD3A

DC90 HY90

3t

35W4 HL92

30 31

50C5 E92CC EC92

43

32 33

34 35 38 39 3+ 4A 4E 4F 4G 41 4J 4M 4N 4P 4R 4S

UC92 9AB4 EAA91 EB91

5P 5R 5S

6AL5 DK93 K50A 6BZ6 ECF80 6BL8 UCC84

5T 5U 5V 5X 5Y 5Z

PY31

EF74 CV521 LL508

5d 5f 5k 5m

EF83 UCH80 CV5029 MX112 MX115 CV2246 EBF80

4U

EY82 6N3 EC93

4W

HL94

5W

5r 5t 51 52 53 54 55 56 57

ECF82 6U8

59

CV5065 4d 4f

100117 PY81 Bee

4k

K51A

4r 41 43

6A

6263A

6B 6C 6D 6E 6H 6J

PL36

25E5 44 45 47 48 49 4+

UY92 UL44 EB4

65

M8162

8W

PL820

66 67 68 69

VX8162C EL85 min 4383

8Y

CV4050 PEN-A4

UL84 Bee PZ30

UCF80

5726 6AL5W

UL46

UR1C

E91AA

6+

UBF80 HCH81 en 01DAF 75B1 95A1 DM71 1N3 also

EL802 CV4010 CV4014 CV4025 M8079 7247

DCF60 DF61 DF63

7B 7C 7D 7E 7F 7H 7J 7L 7M 7R 7S 7T 7U 7W

7X 7Y 7Z 7d

6SJ7GT 5U4G R1 99899

PCL82 16A8 DF97 1AN5 DC96 M8163 E88CC 6922 17ECCdev 5X4G

5Z4G 5Z4GT 6BG6G 6J7G

6J7GT 6K7G

6K7GT 6K8G M2EC

7k

6K8GT

PL38M

GC10B

7m

6Q7G

2A

DDB32 MX103 MX120 MX122 MX123 MX124 MX125 MX126

7r 7t 70 71 76 7+

6Q7GT

8A 8B 8C 8D 8E 8F 8G 8H 81

12J7GT 12K7G

CV1863 5Z4GT CV2748

6L 6M 6N 6P 6R 6S 6T 6U

Z50T

51

50EH5

6W

M8097

5K

ECC33

5L 5M 5N

ECC34 EF37

6X 6Y

CV2742 CV4015

6Z

M8161 CV4031 M8081

5A 5C 5D 5E 5F 5H

CV9 XY81 HCH81 QE04/10

EL33A

E180CCBee

12J7G

3AU6 39EF

5876A 18503

12K7GT 12K8G 12K8GT 12Q7G

CV4034 12Q7GT

E81L en

CV4007 35Z4GT 35Z5G

CV2204 C3m R20F EF86

6267 8Z 8d

PY32 CCH3 Mull

8f

E90F

8k

7693 PY88 30AE3

EL180

18512

25Z6G

CV5232

55395

7f

6K

12SJ7GT

19BG6G 25Y5G

PEN36C PL33

ME1400

ME1201AG Z303C

CCH3

8K

EL822 VX8124 VX8182 VX8136C VX8137C CV4004

M8083

OG82 dev EM71

EZ36 11EZ

6r 60 62 63 64

M8100 5+

6f

8L 8M 8P 8R 8S 8T 8U

17C8

30A5 4X

EL38M EL820 EY84 6374 IW4-350

8m 8r 8t

DDC38 95108 EZ81

6CA4 88 9A 9B 9C 9D 9E 9F 9G 9H 9J

5893A 5Z3

6AS5 6A7

6C5GT 6F6GT 6J5GT 6AS6 6L6G

9K

VX8084 6L6GA

9L 9M 9N 9P 9R 9S 9V

6X5 25A6G 42 PP35 PP36 PP60 5840

9Z 9k 9m 9r 9t 90 92 93 97 99 *C *T *U

CV3929 Z500E UY82

EL41 A tech EF86 en PY83 ET51

CV2469 VCRX437C

QQV04-16 MX152 Z70U Z700U Z521M Z522M

44

T h re e sy m b o l ty p e co d es AAA AAB AAC

PL509 LL802

AAF

ECF80A 6GH8A EL509 6GK6A LL509 XL509

AAG

N30EL

AAD AAE

6LF6 AAH

10GK6

AAK

6HT5 CV9620

ML AAM AAN AAP

3HQ5

ACN ACR ACS ACT ACU ACV ACW ACY ACZ

ADA

6HQ5 ECF202

6AJ9 AAR AAS AAT AAU AAV

ACL ACM

PCL805 Siem

27LF6 7586 5893

6263 AAW 6264

PB1 D3a 7721 5876

6FQ7 12AD6A 12BX6

25AV5GA 20LF6 XCF80A 8AF9 ECC801S

40LF6 7984

ADB ADC ADD ADE

CV6189 PY500A

ADF

EY500A LY500A XY500A

ADG ADH

EL91N 15GK6

ADK

N25PC

AAX AAY AAZ

5676 5687 5751

ADR ADS ADD

N20PL PCF808

ABA

7587

AEA

16AF9

ABB ABC ABD

50B5 1817 N1EFL

AHA

PD510

MCH MCT MER MES MET MEU

CV6189 PL95 TH2 YL1220 ZP1080

MEW MEX MFC MFD MFF MFZ

K81A

6AF9 ABE ABG

5963

ABK

5642 12BY7 12AT5

ABL ABM ABP ABR ABS

6264A

5R4GY ECC8100 12AU7WA

6189 ABT EL805 ABU ECL805 ABV LD500 ABW XD500 ABY CV4110 ABZ

CV4111

ACB

DW4-500

ACC ACD ACE

EF800 EF802

ACF

EL521

ACG ACH

EL802 EL803 EL803S

ACK

MGC MGF

6LV6

ZP1081 N54RPY

6D4 CV287 N55RPY

CV359 VX8250 VX8252

6CF6

45

The Brent Jessee Recording & Supply, Inc http://www.audio tube s .c om /

Telefunken Tube Date CodesSource Material from Eric Barbour Originally presented in "Tube Collector" Vol.2 No.4 This list shows date codes covering Telefunken tube production between 1930 and 1968. This chart had originally come from a tube enthusiast in Europe; the German- titled chart had been retitled in English. Setting-up the original information in straight "decode" format, we get the table below. Some of the identifications are unclear, what with smudging of the original, and are marked. A few dates are missing. The code uses pairs of lower-case letters a-z (less j), plus (to a limited degree) ä, ö, and ü. As a special case, for postwar Berlin-produced tubes (Berliner Röhre), the uppercase letters A and B are added. A great many letter combinations are not used. The code was random in some years. Later, the three months of a given quarter share a common first letter, and the second letters are normally in ascending order. Thus the months of 1955 are coded aq, as, at; ba, bc, bf; ca, cc, cd; db, dc, dh. However, the letter sequence was sometimes reversed, so that for 1944 the months ran ka, na, la; fk, bk, ck; ad, gd, rd; fv, mv, uv. The months MayDecember, 1945, all lack codes, a sign of the then-times, and a hint that this code gives month of manufacture, not of warranty expiration. I wis h to thank Eric Barbo ur and The Tube Co lle c to r fo r this data. This is pre s e nte d fre e o f c harg e , and fre e o f a ny c o mm e rc ia l e ndo rs e me nt o r purc has e o blig atio ns , inte nde d fo r us e by indiv idual o r c lubs o f v ac uum tube c o lle c to rs to aid in the ide ntific a tio n o f Te le funke n date c o de s . With this in m ind, Bre nt J e s s e e Re c o rding make s no c la im as to the final a c c urac y o r c o m ple te ne s s o f this lis t, and is no t re s po ns ible fo r any c irc um s ta nc e s o r lo s s e s (whe the r c o mm e rc ial o r priv ate ) a ris ing fro m the us e o f this lis t. Pre s e nte d "as is " and "as fo und".

46

A

B

C

D

E

F

G

H

ää 11-43 äa 9 -67 äk 4-43 äz 6-43 aa 6 -35? aA 1-46 aB 2-46 ab 4-31 ac 1 -49 ad 7-44 ae 4 -32 af 2-49 ag 5 -32 ah 7-47 ai 5-31? ak 6-32

ba 4-55 bb 10-67 bc 5-55 bd 10-46 be 10-52 bf 6-55 bg 7-61 bh 8-61 bi 9 -61 bk 5-44 bl 11 -67 bm 12-67 br 5 -41 bt 11-52 by 12-52

ca 7 -55 cb 10-49 cc 8-55 cd 9-55 ce 9-33 cf 1-30 cg 1 -36 ch 12-49 ci 10-61 ck 6-44 cl 11-49 cm 11-61 cn 12-61 co 7 -33 cp 2-30 cq 1-68

da 2-31 db 10-55 dc 11-55 dd 1-62 de 7-30? df 2-36 dg 9-30 dh 12-55 di 2 -62 dk 4-38 dl 3 -62 dm 1-31 dn 3-31 do 4-68 dp 5-58? dq 5-68 dr 9 -39 dt 7-36 du 6-30? dw 8-47

ea 1 -56 eb 10-53 ec 2-56 ed 3-56 ee 4-61 ee 4-62 ef 5-62 eg 6 -62 eh 8-58? ei 2-34 ek 11-30 el 10-36 em 11-53 en 1-34 eö 3 -34 eo 8 -68? ep 2-45 eq 9-58 er 10-30 es 12 -30 et 9-47 ez 12-53

fa 1-53 fb 4-56 fc 1-54 fd 5-56 fe 6-56 ff 8-46 fg 7-62 fh 3-40 fi 8-62 fk 4-44 fl 9-62 fm 2-53 fn 10-68 fo 2-39 fp 2-54 fq 11-68 fr 12-68 fu 7-42 fv 10 -44 fw 3-54 fx 3-53 fy 2-42 fz 9-41

ga 4 -50 gb 10-51 gc 7 -56 gd 8-44 ge 8 -56 gf 9-56 gg 10-62 gh 11-62? gi 12-62 gm 5-50 go 10-47

ha 10-56 hb 11-56 hc 7-50 hd 10-33 he 11-33 hf 7-46 hg 10-38 hh 12-56 hi 6 -39 hk 8-50 hl 3 -63 hm 2-63 hn 3-63? hr 12 -33 hu 9-50

al 5-35 am 4-36 an 4-35? ao 3 -49 ap 1-45 aq 1-55 ar 1-39 as 2-55 at 3-55 au 6-31? av 4 -61 aw 5-61 ax 6-61 ay 7-67 az 8-67

cr 5-46 cs 8-33 ct 2-41 cu 2-68 cv 3 -68 cw 3-30 cy 10-40 cz 4-41

gr 6-50 gt 4-45 gu 1-38 gy 12-51 gz 11-51

I

K

L

M

N

O

P

Q

ia 7-37 ib 4 -33 ic 5-36 id 6 -33 ie 1-57 if 4-53 ig 2-57 ih 3 -57 ii 5 -40 ik 4 -37 il 4 -63 im 5-53 in 5 -33 io 5-61? io 5-63 ip 4 -39 iq 6 -63 it 11-47 iu 2 -40 iv 6-53 iy 1-43 iz 11-42

ka 1-44 kb 1-50 kc 4-54 kd 12-46 ke 2-37 kf 9-40 kg 11-37 kh 2-50 ki 4 -57 kk 10-41 kl 12 -32? km 10-42 kn 5-57 ko 11-32 kp 5-54 kq 6-57 kr 4 -42 ks 7-63 kt 8-63 ku 10-32 kv 5-39 kw 6-54 kx 9-68? ky 3-50 kz 11-40

la 3-44 lb 7 -57 lc 8-57 ld 9 -57 le 2-33 lf 10-63 lg 11-63 lh 12 -63 ln 3 -33 lr 6 -46 lt 1-33l lx 11-39

ma 10-57 mb 11-41 mc 1-51 md 11-57 me 3-32 mf 8-42 mg 4-47 mh 12-57 mi 1-32 mk 4-40 ml 1-64 mm 2-51 mn 2-32 mo 2-64 mp 3-64 mv 11-44 mw 6-38 my 3-51 mz 6-42

na 2-44 nb 1-58 nc 2-58 nd 3-36 ne 3-56 nf 4-64 ng 5-64? nh 5-64 nn 7-39 nr 4 -46

öz 5-43 oa 5 -30 ob 8-39 oc 4 -58 od 5-58 oe 12-34 of 12 -47 og 6 -58 oh 7-64 oi 1-41 ok 2-38 ol 8-64 om 3-41 on 6-30 oo 12-41 op 9-64 or 11-34 ot 10 -34 ou 4-30

pa 10-39 pb 7-58 pc 8-58 pd 9-53? pe 10-64 pf 11-64 pg 5-47 ph 12-64 pn 7-34 po 8-36? pr 9 -34 pt 6-40

qa 10-58 qb 11-58 qc 12-58 qd 1-65 qe 2-65 qf 3-65 ql 3 -47 qr 2 -47 qz 1-47

47

R

S

T

U

V

W

X

Y, Z

ra 1-48 rb 1 -59 rc 2-59 rd 9-44 re 9-32 rf 9-36 rg 10-50 rh 11 -50 ri 8 -37 rk 8 -41 rl 3 -59 rm 4 -65 rn 12 -50 ro 5-65 rp 3 -45 rq 6 -65 rr 7 -32 rs 8 -32 ru 11 -38 rw 2 -48 rx 3 -48 rz 1 -42

sa 4-52 sb 4-59 sc 5-59 sd 6-59 se 11 -35 sf 5-37 sg 5-52 sh 7-65 si 1-40 sk 12-35 sl 9-48 sm 8-48 sn 8-65 so 7-48 sp 10-35 ss 3-37 st 12-38 su 3-38 sy 6-51

ta 8-35 tb 8-40 tc 8-31 td 7-53 te 7-31 tf 7-59 tg 6-47 th 8-59 ti 9-59 tk 10-65 tl 6-35 tm 8-53 tn 9-31 to 11 -65 tp 12-65 tq 6-41 tr 7-35 tw 9-53

端k 3-43 端端 12-43 ua 11-48 ub 10-59 uc 11-59 ud 12-59 ue 1-66 uf 7-52 ug 12-32 uh 11-31 ui 7 -43 uk 8-43 ul 9 -38? um 3-42 un 10-48 uo 12-48 up 2-66 uq 3-66 ur 8 -52 uv 12-44 uw 9-52 uy 7-41 uz 10-31

va 4 -49 vb 1-52 vc 7 -54 vd 3-40? ve 1 -60 vf 2-60 vg 3 -60 vh 6-36

wa 9-37 wb 5-38 wc 4-60 wd 5-60 we 12 -39 wf 8-38 wg 8-51 wh 7-51 wi 6-37 wk 4-48 wl 6-60 wm 9-51 wn 7-66 wo 12-37 wp 5-48 wq 8-66 wr 9 -66 wt 6-48

xa 5-34 xb 7-36? xc 10-54 xd 7-60 xe 4-34 xf 9-46? xg 8-60? xh 6-34 xi 9-60 xk 10-66 xl 11-66 xm 12-66 xp 11-54 xr 7 -40 xw 12-54 xy 9-42

ya 10-60 yb 11-60 yc 12-60 yd 9-49 ye 2-35 yf 1-67 yg 2-67 yh 3-67 yi 5-42 ym 8-49 yn 3-35 yq 12-40 ys 1-35 yt 7-49

vi 4-66 vk 6-49 vl 5-66 vm 2-52 vn 6-66 vp 8-54 vr 5-49 vs 7-38? vt 3-52 vw 9-54 vz 11-36

zb 1-61 zc 2-61 ze 3-61 zf 4-67 zm 5-67 zn 6-67 zu 10-43 zw 5-51 zz 12-42

48

And about those codes?

The code systems for vacuum tubes are among the best code systems ever invented. Initially different branches give serial number for the tubes in their catalogue. Quickly it became confuse because the number said noting about the tube and different branches could give the same number for different tubes. Until today there are same branches that give special codes for their tubes, like Svetlana ,but most tubes are referred through the American (RCA) or European (Philips) code systems.

Some people prefer to use the European code and others prefer the American. I use both. Some times a specific type is popularly known by its European code, like EL84 (6BQ5 in America), others are known by its American code, like 12AX7 (ECC83 in Europe). I am more familiar with the European code so let me explain this one first.

The European code The European code always begins with a number of letters followed by figures. The first letter is related to the filament rating according to the following table.

A – 4V C – 200mA D – 1.4V (usually from batteries) E – 6.3V F – 12.6V G – 5V H – 150mA for series connection K – 2V (usually from batteries) L – 450mA for series connection O – Cold cathode P – 300mA for series connection U – 100mA for series connection V – 50mA for series connection X – 600mA for series connection Y – 450mA for series connection Z – Cold cathode (usually a gas diode for tension reference) The second and subsequent letters mean: A – R.F. single diode B – R.F. double diode C – Triode (except output and gas filled triodes) D – Output triode E – Tetrode (except output tetrodes) F – Pentode (except output pentodes) H – Hexode or heptode K – Octode or heptode L – output tetrode or pentode M – Tuning indicator (Rarity. If you have one keep in a safe place) P – Tube with secondary emission system Q – Enneode S – Scanning valve for television T – Miscellaneous X – Full-wave gas filled rectifying tube Y – Half-wave high-vacuum rectifying tube Z – Full-wave high- vacuum rectifying tube The figures are serial numbers related to the valve base according to the table 1 to 10 – Side contact base 11 to 20 – Footless 8 -pin Telefunken Base 21 to 30 – Loctal 8-pin 31 to 39 – Octal 40 to 49, 140 to 149 – Rimlock base.

50 to 59 – P base 60 to 69 – Enne-al base 70 to 79 – Subminiature 8-pin 80 to 89 – Noval 90 to 99 – Miniature 7p .

49

The American code The American code consists of digits, a group of letters, more digits plus and an optional suffix.

The first digits give the filament voltage. Digit 0 denotes cold cathode, 1 between 0.1 and 2.1, 2 between 2.1 and 2.9, 3 between 3.0 and 3.9, 5 between 5.0 and 5.9, 6 between 6.0 and 6.9, and so

on.

The exception is that codes 7 and 14 are ‘nominal’ voltages and are used to indicate 6.3V and 12.6V valves with a loctal base. But one can find codes like 7AU7 that is a version of valve 12AU7 for connection in series with 0.6mA current and actually has a filament for 7V. In the case of tapped filaments or heaters the first figure indicates the total voltage with both sections in series. The 12AX7 valve, for example, may be connected in 12.6V between pins 4 and 5 or 6.3V between pins 4+5 and 9 The second symbol is a letter, which is allotted in sequence commencing with A. The letters “I” and “O” were never used to avoid confusions with the digits 1 and 0. Rectifier tubes follow the sequence backward staring at Z. When all the single letters of a group are exhausted, the system then proceeds with two letters commencing with AB; combinations of identical letters are not normally used. The single-ended (no top cap) alternating current has a first letter S while the second letter may be that of the nearest equivalent in the double-ended range – e.g. type 6SK7 is the nearest single-ended equivalent to type 6K7. Another special case is the first letter L that is used for lock-in (loctal) types in the battery range. P as a second letter indicates a cathode ray tube.

The rectifiers all start at the end of the alphabet like 5Z3, 35Z5, 5X4, 5U4 etc.

Second digits give either the number of active electrodes or elements, or else the number of external connections. In metal tubes the shell counts as one element. Shielding by or in the base does not count as an element.

Whenever possible the 12V equivalent of a 6V tube retains the same letters, thus 6SK7GT and 12SK7GT are similar except for the heater rating.

The suffix letters specify the type of envelope or base. The code is: G - large Glass envelope on octal base GC - Glass Compact, a tubular glass envelope GT - Glass Tubular, the smallest glass envelope GT/G - Glass Tubular, interchangeable with G and GT types LM - Loktal-metal LT - Locking base M - Metal-coated glass envelope on octal base MG - Metal-glass ML - Metal-loktal S - Spray-shielded (zinc-clad) W - Military type assigned on behalf of armed forces, ruggedised X - Low-loss base for HF use (ceramic) Y - Intermediate-loss base (mica-filled phenolic) A, B, C, D, E, F modified version of a type without other suffix (note 2) Note 1: Valves used specifically for industrial purposes have a sequential all-numeric designation.

RCA used 1600 numbers for special purpose/industrial tubes, and Sylvania used 1200 numbers.

Note 2: Devices calling for the A versions of the tube may really need them. The canonical rule is that higher suffixes replace lower suffixes (or no suffix at all), but not vice-versa. Then again, that might just of been the current version at the time of design. In some A tubes, the A indicates things like higher anode dissipation, particularly in the case of power tubes. In other cases, the A means controlled heater warm-up time for series-string filaments

50

CV codes All the UK military spec valves that were used by the War Department all had a CV (Common Valve) number and have always had a strange code inked on to the glass usually in the form of KB followed by a slash ( / ) followed by one or two letters i.e. KB/DA (I have also seen just the slash followed by a one or 2 letter code). This code as always been a mystery to me but the other day I was looking through some old copies of “The Radio Constructor” (ranging from 1951 to 1959) that a friend of mine had had inherited some 15 years ago and had given them to me and inside one was hand written in pencil the following : (I think this is correct but 30 to 40 year old faded pencil on 40 to 50 year browning paper is quite hard to read)

KB/AD......Thorn-AEI (Brimar).........................Rochester KB/D.......Mullard Radio Valve Co. .................. Mitcham KB/DA......Mullard Radio Valve Co. .................Blackburn KB/F .......STC (Standard Telephone & Cable Co.)....Paignton KB/FD......STC ............................................Rochester KB/FE......STC ............................................Oldway KB/FB ......STC ............................................Footscray KB/N.......STC (before 1952)..........................Footscray KB/K .......Electronic Tubes ............................High Wycomb KB/L.......M.O. Valve Co. (Before 1952) KB/Z.......M.O. Valve Co. ..............................Hammersmith KB/ZA......M.O. Valve Co. (Before early 1957)...Gateshead KB/Q.......English Electric Valve Co. ................Chelmsford KB/R.......Ferranti .........................................Moston Can’t verify if they are correct but the KB/DA checks out with my box of CV492’s, which are factory stamped 12AX7XL, B6K2, I63.

CV marked valves usually carry a code to indicate the manufacturer and where the pumping process was completed. The following table lists these codes:

Code A A AB AC AD B BA BC C CC CE CF CN CO CS D DA DB DC DE DF DG DH E

Manufacturer Mullard Radio Valve Co., Thorn Sylvania- Thorn Thorn-AEI Thorn-AEI (Brimar) Edison Swan AEI (Asssociated Electrical Industries Ltd.,) Joseph Lucas Edison Swan Cathodeon 20th Century Electronics 20th Century Electronics Pye Industrial Electronics Newmarket Transistors Cathodeon Mullard Radio Valve Co., Mullard Radio Valve Co., Mullard Radio Valve Co., Mullard Radio Valve Co., Mullard Radio Valve Co., Mullard Radio Valve Co., Associated Semiconductor Manufacturers Societe Anonyme Philips Thorn-AEI

Factory Blackburn (prior to January 1951) Tottenham (prior to April 1964) Enfield Footscray Rochester Baldock (prior to September 1945) Woolwich Birmingham Ponders End (prior to September 1951) Cambridge New Addington (prior to March 1957) New Addington @ Newmarket Southend Micham Blackburn Salford Whyteleafe Fleetwood Waddon Southampton Brive, France Brimsdown 51

EA EB EC EN F FB FC FD FE FF G GA H HC HR J J JA JB JD JE JK JN JQ JT K L L LB M MA MB MB MR MT N N NP NQ NR O OR OS P P PA PDA Q QB QC QD QE QF R R RA RB RC S SA SB SC

Edison Swan Edison Swan Edison Swan Thorn-AEI STC (Standard Telephone and Cable Co.,) STC (Standard Telephone and Cable Co.,) STC (Standard Telephone and Cable Co.,) -Lorenz STC (Standard Telephone and Cable Co.,) STC (Standard Telephone and Cable Co.,) STC (Standard Telephone and Cable Co.,) Ericsson AB Svenska Elektronror (Ericsson) Hivac Hivac Hivac STC (Standard Telephone and Cable Co.,) Radar Electronic Equipment SGS Fairchild SGS Fairchild Elliott Bros. (London) Ltd., Elliott-Litton La Radio Technique International Rectifier Co., (GB) Ltd., Associated Transistors Microwave Associates Ltd., Electronic Tubes CSF (Compagnie G ale de T.S.F.) MO Valve Co., CSF Gramophone Co., EMI Research Labs., EMI Research Labs., EMI EMI (Valve Division) EMI Nore Electric STC (Standard Telephone and Cable Co.,) Texas Instruments Texas Instruments Texas Instruments Rank Cintel Rank Cintel Rank Cintel Philips GEC (General Electric Co., Ltd.,) Philips Teleindustri Philips EEV (English Electric Valve Co.,) MWT (Marconi Wireless Telegraph Co., Ltd.,) MWT (Marconi Wireless Telegraph Co., Ltd.,) EEV (English Electric Valve Co.,) EEV (English Electric Valve Co.,) EEV (English Electric Valve Co., ) (Nelson Research Labs) Ferranti Ferranti Ferranti Ferranti Ferranti AEI (Asssociated Electrical Industries Ltd.,) AEI (Asssociated Electrical Industries Ltd.,) AEI (Asssociated Electrical Industries Ltd.,) CFTH

Ponders End Gateshead Tottenham Sunderland Paignton Footscray Esslingen, Germany Rochester Oldway (additional to Paignton Factory 'F') Harlow Beeston Stockholm, Sweden Harrow Chesha m Ruislip Crewkerne (prior to January 1946) @ Ruislip Agrate, Milan, Italy Borehamwood Borehamwood Suresne, Paris, France Oxted Ruislip Luton High Wycombe Levallois-Perret (Seine), Paris, France (prior to Oct. 1951) St., Egreve, Grenoble, Lsere, France Hayes Hayes Ruislip Hayes Ruislip Treorchy Southend Footscray (prior to August 1951) Dallas Road, Bedford Bedford Nice, France Lower Sydenham Rotunda Sidcup Eindhoven, Holland Shaw (prior to August 1951) Stockholm, Sweden Hendon, Australia Chelmsford Great Baddow Chelmsford Stafford Kidsgrove Hixon Moston Gem Mill (prior to July 1947) Edinburgh Dundee Chadderton, Oldham Rugby Lutterworth Lincoln Usine de Joinville, Seine, France 52

SD SDA SF SL SP T U U V V VA VF VL VR W WB WD WE WF X Y YA YC YD Z ZA ZB ZC ZD ZE

SESCO AWV (Amalgamated Wireless Valve Co., Pty Ltd.,) CFTH AEI (Asssociated Electrical Industries Ltd.,) AEI (Asssociated Electrical Industries Ltd.,) British Tungsram MO Valve Co., Nucleonic and Radiological Cossor Gilbert Photelectrics Westinghouse MCP Electronics Hughes Internations (UK) Ltd., Brucsh Crystal Co., GEC (General Electric Co., Ltd.,), Hirst Labs GEC (General Electric Co., Ltd.,) Claude General Neon Lights ASM Ltd., ASM Ltd., MO Valve Co., MO Valve Co., Leigh Electronics Semiconductors Ltd., Semiconductors Ltd., MO Valve Co., Marconi- Osram MO Valve Co., Marconi- Osram MO Valve Co., Marconi- Osram MO Valve Co., Marconi- Osram MO Valve Co., Marconi- Osram Osram GEC Lamp Works

Rue de L'Amiral, Mouchex, Paris, France Sydney, Australia Rue Mario-Nikis, Paris, France

Leicester Peterborough Tottenham (prior to October 1945) Strafford Highbury (prior to September 1945) @ Chippenham Alperton Glenrothes Hythe Wembley Coventry Wembley Hazel Grove Broadstone Springvale (prior to October 1951) Moray (prior to April 1945) Havant Cheney Manor, Sweden Towcester Hammersmith Gateshead (prior to March 1957) Perivale Springvale (prior to August 1957) Dover (prior to December 1956) MXT Dept (prior to March 1957)

Codes US VT (Valve Tube) : JAN (Joint Army Navy) C CAA CADK CAGE CAGX CAHG CAPQ CBBM CBNQ CBQZ CBUP CBW CDN CDR CDU CDZ CEL CEP CFN CFT CG CHS CHY CIM CIY

National Electronics

CIZ

Arcturus Kuthe Labs American Telev. Inc. Waterman Prod. Co. Chatham Electronics Arpin Mfg Victoreen Bomac Labs Rauland Thomas Electronics Duovac Daven General Electronics Du Mont Electronic Enterprises Electrons Inc. Ampertex Farnsworth Te. & Radio Federal T.& R. Co. GE Sylvania Hytron/ CBS-Hytron Eimac Rauland

CJEA CJR CK CKH CKR CMW CNU CNY COZ CQ CRC CRP CRS CRS CS CT CTL CTY CUE CVG CW CWL CYN

Ind'l & Comm'l Elect.

Bendix Red Bank

Johnsonburg Canadian Westinghouse Heintz & Kaufman Ken-Rad Majestic National Union/ Landsdale Tube Co. North Am. Philips Sonotone Corp.

Rogers Elect. Corp.

RCA Raytheon Cable (Speed) Champion Sperry Gyroscope Co. Northern Electric Tung- Sol Taylor Tubes Inc. United Electronics Electr. Tube Corp/ General Atronics Western Electric Westinghouse Lewis Electronics

American VT (Valve Tube) :

53

Valve Numbers and how to decode them -----------------------------------European system, also known in Britain as the Mullard Code Two codes are used, one for transmitting and industrial valves, the other for receiving valves. Both consist of a string of two or three letters followed by a

series of digits, for example ECC83, EL34.

TRANSMITTING VALVES First letter (general class of valve) M LF power amplifier or modulator triode

P RF power pentode Q RF power tetrode R Rectifier T RF power triode Second letter (type of cathode) G Oxide-coated filament in mercury- vapour rectifier V Indirectly heated oxide-coated cathode X Directly heated pure tungsten filament Y Directly heated thoriated tungsten filament Z Directly heated oxide-coated filament (except in mercury-vapour rectifiers) Third letter S Silica envelope First number (anode voltage in kV) followed by hyphen 05 0.5kV

5 5kV 12 12kV and so on Second number (output) For valves up to 5kW anode dissipation, the figures indicate maximum anode dissipation in watts.

For water-cooled valves above 5kW dissipation, the figures indicate the maximum output in kW. For rectifiers, the figures indicate the maximum permissible rectified current per valve in

milliamps.

RECEIVING AND GENERAL PURPOSE VALVES

First letter (heater rating) A 4V B 180mA DC series connection C 200mA AC/DC series connection D 1.4V DC (normally directly heated, can also be 0.625, 1.2 or 1.25V) E 6.3V (by far the most common prefix) F 12.6 or 13V G 5V, later defined as ‘miscellaneous voltages’ H 150mA series connection K 2V DC L 450mA series connection (?)

O cold device, not heated, e.g. cold cathode tube, voltage stabiliser or semiconductor device P 300mA AC/DC series connection U 100mA series connection V 50mA series connection X 600mA series connection Y 450mA series connection

54

The second and where applicable, third and fourth letters in

multi-electrode valves indicate the types of device in the valve. They are normally listed in alphabetical order.

A Signal diode B (=AA) double diode C Signal triode D Output or power triode (e.g. TV shunt stabiliser) E Signal tetrode F Signal or RF pentode H Hexode or heptode (Hexode structure) K Heptode or octode (octode structure) L Output tetrode, beam tetrode, or pentode (including TV line output valves) M Magic eye tuning indicator N Gas-filled triode or thyratron Q Nonode X Full-wave rectifier or double diode (gas-filled) Y Half wave rectifier or single diode (vacuum) Z Full-wave rectifier or double diode (vacuum) Digits indicate the base (first digit) and a code to distinguish valves

that would otherwise have identical numbers (e.g. EL84 and EL85 are both output pentodes with a 6.3V heater on a B9A base. They are otherwise different).

1 - 10 side contact 11 - 20 footless 21 - 30 Loctal 31 - 39 and 300 series International Octal 40 - 49, 140 - 149 B8A 60, 70 Subminiatures 80 - 89, 180 and 800 series B9A 90 - 99 B7G 200 series B10B 500 series B9D GEC Code (Marconi/Osram Brands also) Consist of Letter (or Letters) followed by digits (e.g. L63, KT88). The

digits are simply to distinguish similar valves (like all triodes), and cannot be decoded. The letters have the following meaning.

A Industrial valve (Maybe almost anything - power triode, etc.)

B Double triode D Diode GU Gas-filled rectifier GT Gas Triode (Thyratron) H Signal triode (high impedance) KT Kinkless tetrode (beam tetrode) L Signal triode (low impedance) MU Indirectly heated rectifier N Output pentode P Output triode QP Quiescent push-pull double pentode S Tetrode (Screen Grid Valve) U Rectifier VS Variable mu tetrode W Variable mu pentode X Triode hexode, heptode, octode, frequency changer Y Tuning indicator Z HF pentode 55

USA (Radio Manufacturers Association) This code consists of digits, letters, digits plus an optional suffix. A variant is used by

the Russians.

The first digits give the heater voltage rating, with the exception that

the codes 7 and 14 are used to indicate 6.3V and 12.6V valves with a loctal base.

Not all tubes follow the rules; for instance 1F4 has 2V heaters and 2C22 has 6.3V heaters.

Letters specify the type of valve, but there appears to be no consistency

of coding. S often indicates a single-ended (no top cap) version of an earlier valve with such a cap Second digits give either the number of active electrodes, or the number

of external connections.

The suffix letters specify the type of envelope or base. The code is G large Glass envelope.

GC Glass Compact, a tubular glass envelope GT Glass Tubular, the smallest glass envelope LT Locking base M Metal envelope WA High quality version Mazda Code (Great Britain) Consists of digits, Letters, digits. Do not confuse with a US code.

First digits give heater voltage, except that 10, 20, 30 indicate 100mA, 200mA,

300mA for series connection Letters give type of valve C Frequency changer D Signal diode F Signal tetrode/pentode K Thyratron L Signal triode M Tuning indicator P Output tetrode/pentode U Half wave rectifier

UU Full wave rectifier.

Mazda codes tend not to double up letters - L is used for multiple triodes also.

Final digits distinguish between otherwise identical codes.

British Royal Air Force Code consists of letters followed by digits. The letters have the following meanings : VCR - valve cathode ray (CRT) VGT - valve gas triode (thyratron) VI - valve indicator (tuning eye) VR - valve receiving (general receiving valve) VS - valve stabilising (gas stabiliser) VT - valve transmitting (general transmitting valve)

56

VU - rectifier British Army Again, letters followed by digits. The letter part gives the valve type as follows : ACR - Army CRT AR - Army receiving valve (generally triode) ARD - Army receiving diode ARDD - Army receiving double diode ARH - Army receiving hexo de ARP - Army receiving pentode ARS - Army receiving screen grid (tetrode) ARTH - Army receiving triode hexode ARTP - Army receiving triode pentode AT - Army transmitting valve (generally power triode) ATP - Army transmitting Pentode ATS - Army transmitting Screen Grid (Tetrode) AU - Army Rectifier AW - Army Stabiliser British Royal Navy Another letters followed by digits code. The letters give the type of the valve, as follows : NC Navy CRT NGT Navy gas triode (thyratron) NR Navy receiving valve NS Navy stabiliser NT Navy transmitting (or power) valve NU Navy rectifier Other B ritish se ries CV (common valve) numbers replaced the above 3 codes during WW2. There is

no way to decode these by simple inspection of their number. ZA and 10E are also used as prefixes to catalogue numbers. For example UHF ‘horned’ triode 10E/392 is also equivalent to ZA 3055, VR 135, NR 80, CV 1135 and E 1148.

French Army Originally numbered in the TM (Télégraphie Militaire) series with the letters TM followed by the type number. There was also an ‘11’ series of all-metal

construction with octal base and equivalent to comparable American types but using 11-volt heaters. Thus 11L6 was similar to 6L6 but using 11 -volt heaters. Valves marked ECMR indicate French army origin (Etablissement Centrale du Matériel Radio-télégraphique militaire.

German Defence (Reichswehr) Most German army valves use a special base and bear codes in the format:

two letters, two digits, one letter and two digits.

First letter R Reichswehr (Defence), includes both Wehrmacht (Army) and Kriegsmarine (Navy)

57

Second letter D Dekametric wavebands

G Rectifier (Gleichrichter) or diode K Cathode ray tube L Transmitting or Power V Amplifier (Verst채rker) First number Heater voltage Third letter A Cathode ray indicator

D Dual anode G Rectifier or diode H Hexode L Speed modulation M Magnetron P Pentode T Triode Final number This indicates the maximum power output in watts if the valve is a power tube, the coefficient of amplification if an amplifier or maximum rectified current if a rectifier.

A different scheme was used by the Air Force, employing two letters and a

number.

The number is a simple type number, issued progressively as each new valve was registered.

First letter L Luftwaffe (German Air Force) Second letter B Cathode ray tube D Dekametric waves F Special type

G Rectifier or diode K Stabiliser M Magnetron S Transmitting, wavelengths above 1 metre V Amplifier, wavelengths above 1 metre Exceptions to this scheme include SA (rectifier), SD (triode) and SF (pentode), all

using 1.9V heaters.

Mazda (France) Television tubes use the code letter C (for cathode ray tube), a number (indicating screen size in mm), then two letters followed by a number. The first indicates the method of deflection (M = magnetic, S = electrostatic) and the second the screen colour (B = blue, G = green, R = radar long-persistence, W = white). The numbers were allocated sequentially.

58

Min iwatt (France) This is a subset of the European system. Either two or three letters are

used, followed by a sequential number.

First letter (heater) A 4V AC B 180mA DC C 200mA AC/DC D 1.4V battery E AC and 6.3V car battery F 13V car battery H 4V battery K 2V battery U 100mA AC/DC Second and optional third letter (type of valve)

A Diode B Double diode C Triode (oscillator, detector, amplifier) D Audio power triode E Pentode F RF pentode H Hexode or heptode K Octode L Audio power pento de M Visual tuning indicator X Dual-anode rectifier (gas-filled) Y Single anode rectifier (vacuum) Z Dual-anode rectifier (vacuum) Television tubes use two letters followed by a number. The first indicates the method of deflection (D = electrostatic, M = magnetic) and the second the screen colour (B = blue, G = green, R = radar long-persistence, W = white). The numbers

were allocated sequentially.

Telefunken (Ge rmany) This simple code had just two series, RE and RS, standing for Rรถhren-Empfangen (receiving valves) and Rรถhren-Senden (transmitting valves). The three-digit number following indicates first the heater current (first two digits, in hundredths of an amp) then the heater voltage (4, 3, 2 or 1 for 4V, 3V, 2V or 1.5V). The final

letter indicates the valve base pattern, t for Telefunken, d for Europa-base with side contact for space grid, and no letter at all for Europa-base.

American Army (US Army - Signal Corps) VT numbers are USA military valves, with no way of decoding their

pattern without look-up tables, although many valves were dual-marked with VT and civilian part numbers.

BVA numbers (British Valve Association) were assigned to valves used for civilian replacements in WW2.

59

PRINCIPLES OF TUBE TESTING

BK Precision model 747 vacuum tube tester Reproduced with pe rmission by BK Precission

http://www.bkprecision.com/

60

8/5/2008, 12:12:07

DYNAMIC MUTUAL CONDUCTANCE TESTING A. Introduction In radio and television circuits practically all tubes (except rectifiers and diodes) are used as some type of amplifier. Even oscillator circuits (i.e. —R.F. or horizontal oscillators) are basically amplifiers with regenerative feedback. T herefore, the most important characteristic to be checked to determine how effectively any radio or T V tube will function in its circuit, is its ability to amplify. T his, in turn, is governed by its mutual conduc tance.

The mutual conductance is the ratio of change in the plate current that results from a small change in grid voltage.

G m = ? IP/? Eg

where: ? Ip = a change in plate signal current ? Eg = a small change in grid signal voltage.

The amplification of a circuit = G mR L. Where RL is the equivalent load resistance of the stage.

Since RL is constant in any circuit, we see that the amplification depends directly on the G m of the tube.

61

B. Circuit Analysis Refer to Figure 1. T ransformer T l provides the ac grid signal voltage for the G m test. T he signal from the secondary of T l is developed across the bridge network consisting of R22, R23, FL 1 and FL 2. T he bridge network gives automatic line voltage compensation as follows: • An increased transformer voltage causes the lamps to burn brighter and hotter.

• Resistance of the bulbs increase as they become hotter.

• As the resistance of the bulbs increases, proportionally more voltage is dropped across the bulbs and less across the resistors.

• T he signal level at the output of the bridge decreases.

T he opposite conditions apply when the pri mary voltage decreases.

T hus, the network compensates under high line voltage conditions to provide less signal and under low line voltage conditions to provide more signal. T his variation in signal drive compensates lor plate voltage variations so that meter readings become strictly a matter of tube condition, and are not affected by line voltage variations.

Adjustable resistor R21 is a calibration adjustment which sets the signal level. A negative dc power supply circuit furnishes bias voltage for the tube being tested. Bot h si gnal a nd bias are applied to the grid of t he tube under test.

During the Gm test, plate voltage for the tube is alternately provided by rectifier circuits Dl and T l, then D4 and T l. T he plate current path is completed through a bridge network R3, R4, R5 and R6. T he relative G m meter (BAD -?-GOOD meter) is connected across one leg of the bridge net work to sample plate current.

When a resistive load is placed in the tube socket, which represents a tube with zero G m , plate current through the bridge is balanced and the meter reads zero. Plate currents of equal amplitudes but opposite directions give an average current of zero uA. T he G m for a given tube can be measured accurately by applying the correct amount of a.c. signal voltage to the grid and measuring the resulting a.c. plate current. T his is done by means of a sensitive bridge circuit.

Measuring the mutual conductance of a tube provides the most accurate and all inclusive single test that can be made on any tube.

When an amplifying tube is placed in the circuit, the signal voltage is i nphase with one plate transformer winding and out-of-phase with the other plate transformer winding. T he positive going portion of the signal

62

causes the plate current through Dl and Tl to increase, while the negative going portion of the signal causes plate current through D4 and Tl to decrease. The meter reads the difference between the two currents, which is proportional to the GB, of the tube.

C. Dual Section Tubes Refer to Figure 2. Each section of a dual section tube is tested separately. The TEST 1 button checks the section with the most elements.

For example, in a pentode—triode, TEST 1 checks the pentode section and TEST 2 checks the triode section. For tubes with two identical sections such as twin triodes, the two readings are valuable for selecting tubes with balanced sections for push-pull circuits.

TO METER BRIDGE

Fig ure 2. Te s ting o f Individual S e ctions of Dual S e ction Tube s .

DIODE AND RECTIFIER EMISSION TESTING Refer to Figure 3. Diodes have no G m , therefore cannot be given a dynamic mutual conductance test. Diodes are tested by applying an ac

14 Figure 3. Diode and Re ctifie r Emis s ion Te s t

63

voltage to the plate. The rectifying action of the tube allows current to flow only in one direction through the meter and an indication of the tube's emission is measured. Low voltage diodes such as signal detectors use a current limiting resistor to represent actual circuit conditions and to limit current to a safe level. Rectifiers are tested without current limiting to test their current capabilities under actual circuit conditions. High voltage rectifiers are tested from a separate high voltage ac source to complete the full range of dynamic test conditions.

100V

-DC BIAS Fig u re 4 . S h o rts Te s t

SHORTS TEST

Refer to Figure 4. The shorts test applies normal bias voltage to the tube being tested, but grounds the screen while applying a positive dc voltage to the plate and the filament. If any element is shorted to the plate or filament, the resulting current will develop a high potential across resistor R20 and fire the neon SHORTS lamp also, any leakage resistance of 1 megohm or less will cause the lamp to light. If any element is shorted to the grid, grid current will flow and develop a voltage across R12. Such grid current biases field effect transistor Ql into conduction and produces a meter reading in the GRID EMISSION REJECT portion of the scale.

GRID EMISSION TEST A. Introduction The Grid Emission Test is an invaluable aid in TV servicing because it quickly picks out those tubes which can cause trouble in a.g.c., sync, I.F.

amplifier, and R.F. tuner circuits.

In order to understand how a tube can have "grid emission" and "gas current" we must look into the theory of electron tubes.

There is normally some little evaporation of the cathode coating mate-

64

rial on the grid of a tube. Some oi this vapor tends to deposit on the grid and gives rise to what is known as "grid emission", where the grid itself emits electrons and draws current commonly known as "negative grid current".

Figure 5. Crid Emis s io n Currant

T he electrons flow from t he grid to the plate then back through t he power supply to t he grid leak resistor R, and up to t he grid agai n. (See Fig 5.) Notice that the voltage drop across the grid leak resistor R ff is suc h that it causes the grid to go more positive than it normally would with no grid emission.

If a slight amount of "gas" is present in a tube some of the electrons from the cathode will collide with molecules of the gas and may knock off one or more electrons, leaving positive ions (ionization). Some of these positive ions may then strike the grid, taking an electron from the grid to form a gas molecule again. T he electron flow of this "gas current" is exactly the same as it is for the "grid e mission current". Notice again that the grid is made more positive by this "gas current".

Now let us see what happens if an I.F. amplifier tube in a T V set has grid emission current or gas current (ne gative grid current). In Figure 5 we noted that the grid would tend to go more positive if negative grid current flowed.

In Figure 6, a typical I.F. stage, we see that if there is any negative grid current, the bias voltage in that stage and other associated stages will go more positive because of the flow of current through Rl. Because of the high resistance values normally encountered in tube type AGC circuits, very little negative grid current is necessary to cancel the effects of the negative AGC voltage. Making the grid more positive will drive the tubes to saturation, causing clipping or overloading.

65

After detection, a video signal normally appears as shown in Figure 7. if the signal is clipped in an I.F. stage, it will look like Figure 8. Now the horizontal oscillator will try to synchronize both on the blanking signal (A) and on the very black portions of the video (B). This results in pulling or snaking of the picture.

B. Circuit Analysis Refer to Figure 9. A highly sensitive, solid state grid emission test f i r cuit measures leakage as low as i/ 2 microampere (100 megohms leakage resistance). During the grid emission test, normal plate and screen voltages are applied to the tube under test, but a high negative dc voltage is applied to the grid. T he tube is biased well beyond cut-off so that no plate current flows in a good tube. T he meter is driven by a field effect transistor (FET)

66

Fig ure 9 . Grid Emis s io n Te s t

Ql. T his FET is also biased to cut-off, resulting in a zero meter reading.

However, if the tube is gassy or its grid is contaminated with some ot the cathode coating, the negative grid emission flows through resistor R12 and R13 which are also common to the FET gate. T his current causes the gate voltage of the FET to rise in the positive direction, biasing it into conduction and producing a meter reading. T he greater the grid emission current, the greater the meter reading. If the leakage current is excessive the SHORTS lamp will also light.

Diodes are checked for shorts or gas by this test. T he negative dc voltage is applied to the plate of the diode, while its cathode is grounded. Any reverse current will develop a forward bias to the FET and cause the meter to deflect.

A solid state diode across the meter shunts excessive current to protect the meter. More than full scale readings are easily obtained due to the extreme sensitivity of the circuit; therefore, meter protection is required.

Calibration adjustment RIO in the source circuit of the FET sets the sensitivity of this test circuit so that leakage paths of 100 megohms or less will cause the meter to deflect into the GRID EMISS ION-REJECT por tion of the meter.

67

LIF E TEST Refer to Figure 10. The life test will help you judge how much useful life still remains in a tube being tested. A tube may test okay on the Gm test, but the life test will detect whether or not it is in the process of losing its Gm. The test is conducted by holding the LIFE TEST switch in the ON position and repeating the G,,, test.

When the LIFE TEST switch is placed in the ON position, additional windings are connected into the primary which reduces the voltage induced into the secondary windings by 10%. Filament and plate voltages drop. However, the compensating bridge network increases the amount of signal applied to the tube. The meter reading will drop very little if the tube has sufficient reserve to continue to operate normally at reduced heater voltage. In fact, some meter readings will actually increase slightly due to the small increase in signal level. If the meter reading does not drop, the tube is in excellent condition. But if the tube under test has a depleted space charge, a large drop will occur in the meter reading. A drop of 25% of the normal meter reading indicates that the tube is reaching the end of its useful life and should

be replaced.

68

Lis t o f Valve Name s and Manufac ture r fro m 1943

-

(There are probebly moore names)

France

Italy

20th Century Electronics A. B. Svenska Elektronon A. C. Cossor AEI Amalgmated Wireless Valve Co. Amperex Amperex Arctarius AVVT, Prague, Czech Republic B.T.H. Bell Telephone Labs.

Belvu Bendix Bomac Brimar British Tungsram Brown Boveri Burec Canadian Radio Valve CBS Hytron Cetron Champion Cintel CITEL Colomor Compagnei De Lampes (Mazda) Compagnie Generale Telegraphic Corac CSF Dario Dumont E. M. I. (Emitron) East German (manufacturer unknown) Ediswan EI Electronic Industries, Nis, Serbia EI/EI Eltes Eimac Electronic Enterprises Electronic Tubes Electrons Inc. Elektro Harmonix ELLIO Emiel English Electric Ever Ready EVS Federal Union Ferranti G DI SON 69

China

Italy Italy Italy

USA

China

Holland Ukraina

Russian USA

Russian

Russian

China Germany China

General Electric (U.S.A.) General Electric Co. General Electrics Golden Dragon Heinz-Kaufman Hewlett Packard Hivac Hytron Industro JA JJ-Electronics KB/AD Ken-Rad. KR Enterprise, Prague, Czech Republic Kuth Electron Products L. M. Ericsson Lansdale Tube Co. Liuzhou LM Ericsson Manufacturing Corp. Chatham Rogers Majestic Marconi Italians Marconi Osram Valve Co. Marconi Wireless Telegraph Co. Marconi Wireless Telegraph Co. Marshal Matchlett Mazda (Compagnei De Lampes) MU, Oceanside, CA Mullard National Union NU National Union O&J Enterprises/Valve Art Penta Philco Phillips Pinnacle Electronic Products Poljaron, Lvov QTL R.F.T. Radio Corp. of America (RCA) Radio Valve Co. of Canada Reflector Corp, Saratov Richardson Electronics, LaFox, IL Ruby Tubes Ryatheon Ryazan Plant of Electronics, Ryazan S.F.R. SAAB Sans Fil SED Winged C, St. Petersburg SER SF Shuguang Electrical Factory No. 1 Siemens-Ediswan Sino 70

USA

Russian

USA Russian

SL Solus Electronic Tubes (S.E.T.) Sovtek Sperry SRT Standard Telephones & Cables Svetlana /SED Sylvania Taylor Tubes Corp.

Tektronix Telefunken Terma Tomas Triotron Triton Services ETD, Gaithersburg, MD Tung-Sol Tungsram Ulyanov, Ulyanovsk Unknown Japanese Manufacturer Valvo Western Electric (Great Britain) Western Electric (U.S.A.) Westinghouse Westrex Corporation, Kansas City, MO Victoreen Instrument Corp.

Voskhod, Kaluga Zaerix Electronic

71

EL34 - Variants Udo Ra dtke , http://www.tubecollection.de/ EL34 must not be EL34. This is the way how Audio -Freaks separate the tubes in terms of sound. Even when the type lettering on the bulb says "Siemens" the tube must not have been made by Siemens. Especially during the last days of tube production some tube have been produced only at some particular places and companies got them from there with their own brand names.

Therefore I have taken some available EL34 tube variants out of my stock and investigated the differences. Lets start with the anode construction, how are fitted the halves together.

Here are the first spot welding variants with 5 and 7 spots each side. Along the welding lines are at both halves of the sheets small ducts to host a support rod which is welded also to the anodes and supports the system. This rods go through 2 mica insulators, one at top and one at bottom, to keep the system in focussed in the middle of the bulb.

Other tubes have instead of spot welding a crimp fixing. Therefor are punched a number of quadratic holes in the plates. At one side the metal is totally cut out and at the opposit side are bent 2 small flat wings that fit through the

opposit hole for crimping.

Depending on the manufacturer there are different numbers of holes and crimping methods, single sided or reciprocally crimped.

Anodes welded, 2x5

Anodes welded, 2x7

Plates crimped, 2x3

Plates crimped, 2x4

spots.

spots.

holes.

holes.

Anodes crimped reciprocally 2x5

holes.

Another distinctive feature is the size of the slots in the anodes and their position. There are small slots about 6x1mm and big slots about 1,7x6mm. They appear as single slot or two in parallel to each other in distances of 8mm

and 12mm.

1 big slot ca: 1,6x6mm, anode lengh ca: 40mm, here at TFK3

2 small slots ca: 6x1mm, distance ca: 8mm, anode lengh ca: 40mm).

2 small slots ca: 6x1mm, distance ca: 12,4mm, anode lenght ca:40mm).

big slots, ca:1,7x5mm, distance ca: 12mm, anode lenght ca:38mm).

72

Coming now to the different getters. There are:

• disks • plates • 1 halo ring • 2 halo rings • 2 D-getters They are all located without any exeption in the top of the tube. Audio freaks prefer mostly 2 halo rings or 2 Dgetters.

G1- Getter

G2- Getter

G3- Getter

G4- Getter

G5- Getter

The next differeces are in the bases and the glas bulb. First the bases. The main difference is metelbase with black or brown inserts and solid plastikbases in black and brown. The black bases exist in 2 different hights. Some bases have a centerpin with a hole others don`t have any.

So1. Metal base with So2. P lastik base in So3. P lastik base in So4. Different hights So5 Upper tube has black insert) brown black) at black bases) hole in center pin Regarding the glas bulbs are no variations, exept the head. Some have a small dingle downwards. This tube have been produced in East Germany, former GDR. Other variations exist by different shapes of the top and bottom

K1. Dingle in bulb at top

M1. 10 tips in equal spacing among each other

M2. 2x5 tips at top and bottom

M3. 2x5 tips only at top, at bottom none

At least exist variations by different codes giving experianced insiders any note about the company which produced the tube and the year it gas been made. The following pictures show such codes.

73

C1. Code stamped in the metal base

C2. P rint close to the C3. Valvo. Code C4.vertical code at base printed just below the Telefunken tubes B=mullard type.

U=Thorn (BTH)

Next I´m going to establish a table with the 16 investigated tubes in head. Below left I refer to all the differences that I could detect. Then I have colored the cells when a special brand comes across with that details. So I think it will be now possible to check any EL34 tube by this table and to find out which company could have produced it.

Finally I found this info on a forum but I dont know if it works, havn’t tested it ? ”If the markings have gone, don't worry. Put them in the fridge, let them get cold, then blow on them. The markings may well appear as if by magic.

Or use Ammonia if you can put up with the smell.”

74

EIA RETMA Chassis Wiring Color Code In the 1950's the Radio Electronics Television Manufacturers Association (RETMA), now part of the Electronics Industries Alliance (EIA), used color codes to identify electronic parts, such as capacitors and resistors. In addition, there is a lessor-known EIA equipment Wiring Code that identifies the type of circuit each wire serves.

Color - Circuit

Most electronic manufactures of that era, including the popular Heathkit , used this color code for chassis wiring.

When working on antique electronic equipment of that era, this color code can identify circuit wire functions without a schematic or wiring diagram.

Reference verification: Popular Electronics Magazine 1958 July, page 78

75

TESLA About Te s la c o mpo ne nts – c ode with making date Alphabe tc al o rde r. 1947 to the e nd of 1984.

Translated from originalsite

http://www.radiojournal.cz Code

month

Year

AA

7 1 2 3 8 9 4 5 6 4 5 6 7 8 9 1 2 3 1 4 5 3 6 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6

1947 1957 1957 1957 1947 1947 1967 1967 1967 1963 1963 1963 1952 1952 1952 1972 1972 1972 1949 1962 1949 1962 1949 1962 1975 1975 1975 1968 1968 1968 1984 1984 1984 1951 1951 1951 1977 1977 1977

1 2 3 1 2 10 11

1974 1974 1974 1950 1950 1955 1955

AB AC AD AF AH AJ AK AL AM AN AO AU AV AW AX AY AZ BA BB BC BD BE BF BG BH BJ BM BN BO BP BQ BR BT BU BV BX BY BZ CA CB CC CE CG CK CL

76

CM CO CS CT CU CX CY CZ

12 3 4 5 6 1 2 3

1955 1950 1961 1961 1961 1981 1981 1981

DA DB DC DD DE DF DG DH DJ DL DM DN DO DP DQ DR DS DT DW DX DY

10 11 12 7 8 9 7 8 9 4 5 6 4 5 6 4 5 6 1 2 3

1976 1976 1976 1983 1983 1983 1970 1970 1970 1954 1954 1954 1960 1960 1960 1947 1947 1947 1966 1966 1966

EA EB EC ED EE EF EG EH EJ EK EM EO ER ES ET EW EX EY

7 8 9 1 2 3 4 5 6 7 8 9 10 11 12 4 5 6

1971 1971 1971 1979 1979 1979 1965 1965 1965 1949 1949 1949 1952 1952 1952 1959 1959 1959

FA FB FC FD FE FF FG

7 8 9 1 1 2 3

1964 1964 1964 1947 1969 1969 1969

77

FH FL FM FN FO FP FQ FR FT FU FV FW FX FY

2 3 10 11 12 4 5 6 4 5 6 4 5 6

1947 1947 1984 1984 1984 1951 1951 1951 1958 1958 1958 1974 1974 1974

A GB GC GD GE GF GG GH GJ GL GM GN GO GP GQ GR GS GT GU GV GW GX GY GZ

4 5 6 10 11 12 10 11 12 10 11 12 7 8 9 10 11 12 4 5 6

1957 1957 1957

HF HG HJ HK HL HM HN HO HP HQ HR HS HT HU HV HW HX HY

4 5 6 7 8 9 4 5 6 7 8 9 1 2 3 7 8 9

1949 1949 1949 1972 1972 1972 1983 1983 1983 1962 1962 1962 1956 1956 1956 1984 1984 198 4

1969 1969 1969 1947 1947 1947 1979 1979 1979 1963 1963 1963 1973 1973 1973 1952 1952 1952

78

IB IC IG IH IJ IL IM IN IR IS IT IU IV IW

1 2 3 7 8 9 1 2 3 10 11 12 4 5 6

1948 1948 1948 1982 1982 1982 1984 1984 1984 1977 1977 1977 1979 1979 1979

JD JE JF JH JJ JK JN JO JP JR JS JT JU JV JW JX JY JZ

1 2 3 7 8 9 1 2 3 7 8 9 10 11 12

1971 1971 1971 1961 1961 1961 1953 1953 1953

KA KB KC KD KE KF KH KJ KK KL KM KN KO KP KQ KR KS KT KU KV KW KX KY

1 2 3 4 5 6 4 5 6 7 8 9 7 8 9 7 8 9 10 11

1978 1978 1978 1968 1968 1968 1948 1948 1948 1951 1951 1951

IA

1981 1981 1981 1975 1975 1975

1966 1966 1966 1960 1960 1960 1983 1983 79

KZ

12

1983

LA

7 8 9 4 5 6 4 5 6 10 11 7 8 9 12 7 8 9

1959 1959 1959 1956 1956 1956 1976 1976 1976 1949 1949 1965 1965 1965 1949 1979 1979 1979

MB MC MD ME MF MG MH MI MJ MK ML MM MN MO MP MQ MR MT MU MV MX MY MZ

10 11 12 10 11 12 1 2 3 7 8 9 7 8 9 7 8 9 7 8 9

1982 1982 1982 1954 1954 1954

NA NB NC ND NE NF NG NH NI

4 10 5 11 6 12 1 2 3

1972 1948 1972 1948 1972 1948 1977 1977 1977

LB LC LD LE LF LG LH LJ LK LL LM LP LQ LS LT LU LW LX LY LZ MA

1973 1973 1973 1977 1977 1977 1958 1958 1958 1950 1950 1950 1967 1967 1967

80

NJ NK NL NM NN NO NR NS NT NU NV NW NX NY NZ

4 5 6 1 2 3 10 11 12 10 11 12 7 8 9

1953 1953 1953 1982 1982 1982 1970 1970 1970 1963 1963 1963 1957 1957 1957

OA OB OC OD OE OF OG OH OJ OP OR OS OU OV OW

4 5 6 10 11 12 10 11 12 4 5 6 10 11 12

1980 1980 1980 1962 1962 1962 1951 1951 1951 1950 1950 1950 1968 1968 1968

PB PC PD PE PF PG PN PO PP PX PY PZ

7 8 9 7 8 9 10 11 12 -

1948 1948 1948 1976 1976 1976 1961 1961 1961

QA QB QC QD QE QF QJ QK QL QM QN QO QU

10 11 12 10 11 12 10 11 12 1 2 3 1

1966 1966 1966 1980 1980 1980 1960 1960 1960 1975 1975 1975 1955

-

81

QV QW QX QY QZ

2 3 4 5 6

1955 1955 1970 1970 1970

RA RB RC RD RE RF RG RH RI RK RL RM RN RO RP RR RS RT

10 11 12 7 8 9 7 8 9 4 5 6 10 11 12 10 11 12

1972 1972 1972 1953 195 3 1953 1978 1978 1978 1969 1969 1969 1965 1965 1965 1959 1959 1959

SC SD SE SF SG SH SJ SK SL SM SN SO SP SQ SR SX SY SZ

1 2 3 10 11 12 10 11 12 7 8 9 1 2 3 7 8 9

1952 1952 1952 1958 1958 1958 1964 1964 1964 1969 1969 1969 1976 1976 1976 1954 1954 1954

TA

10 11 12 1 2 3 10 11 12 10 11 12 7 8

1967 1967 1967 1964 1964 1964 1957 1957 1957 1978 1978 1978 1973 1973

TB TC TD TE TF TG TH TJ TK TL TM TN TO

82

TP

TY

9 10 11 12

1973 1956 1956 1956

UA UB UC UD UE UF UG UH UJ UL UM UN UO UP UQ UV UW UX

1 2 3 10 11 12 4 5 6 4 5 6 4 5 6 7 8 9

1963 196 3 1963 1974 1974 1974 1982 1982 1982 1971 1971 1971 1955 1955 1955 1980 1980 1980

VA VB VC VG VH VJ VK VL VM VQ VR VS VX VY VZ

10 11 12 4 5 6 1 2 3 10 11 12 10 11 12

1953 1953 1953 1973 1973 1973 1962 1962 1962 1981 1981 1981 1950 1950 1950

WE WF WG WL WM WN WR WS WT WU WV WW

1 2 3 4 5 6 10 11 12

1961 1961 1961 1978 1978 1978

XA

1 2 3 4 5

1960 1960 1960 1966 1966

TW TX

XB XC XD XE

1971 1971 1971

83

XF XJ XK XL XQ XR XS XU XV XW

6 1 2 3 7 8 9 1 2 3

1966 1980 1980 1980 1974 1974 1974 1967 1967 1967

YA YB YC YG YH YJ YM YN YO YP YQ YR YS YT YU

7 8 9 7 8 9 1 2 3 1 2 3 1 2 3

1955 1955 1955 1968 1968 1968 1959 1959 1959 1965 1965 1965 1983 1983 1983

ZA

1 2 3 7 8 9 4 5 6 1 2 3 1 2 3 7 8 9 4 5 6

1970 1970 1970 1956 1956 1956 1981 1981 1981 1958 1958 1958

ZB ZC ZD ZE ZF ZG ZH ZI ZK ZL ZM ZO ZP ZQ ZR ZS ZT ZU ZV ZW ZX ZY ZZ

1954 1954 1954 1975 1975 1975 1964 1964 1964

84

Te s la – Code fo r produc tion data Ris ing o rde r mo nth /ye ar 1947 to 1984.

Code

Month

Year

FD FH FL DR DS DT AA AF AH GL GM GN IA IB IC KH KJ KK PB PC PD NB ND NF BA BC BE HF HG HJ EK EM EO LP LQ LW CE CG CO OP OR OS MT MU MV VX VY VZ BT

1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1

1947 1947 1947 1947 1947 1947 1947 1947 1947 1947 1947 1947 1948 1948 1948 1948 1948 1948 1948 1948 1948 1948 1948 1948 1949 1949 1949 1949 1949 1949 1949 1949 1949 1949 1949 1949 1950 1950 1950 1950 1950 1950 1950 1950 1950 1950 1950 1950 1951

85

BU BV FP FQ FR KL KM KN OG OH OJ SC SD SE GX GY GZ AU AV AW ER ES ET JN JO JP NJ NK NL RD RE RF VA VB VC ZR ZS ZT DL DM DN SX SY SZ MD ME MF QU QV QW UO UP UQ YA YB YC CK CL

2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11

1951 1951 1951 1951 1951 1951 1951 1951 1951 1951 1951 1952 1952 1952 1952 1952 1952 1952 1952 1952 1952 1952 1952 1953 1953 1953 1953 1953 1953 1953 1953 1953 1953 1953 1953 1954 1954 1954 1954 1954 1954 1954 1954 1954 1954 1954 1954 1955 1955 1955 1955 1955 1955 1955 1955 1955 1955 1955

86

CM HT HU HV LG LH LJ ZD ZE ZF TW TX TY AB AC AD GA GB GC NX NY NZ TG TH TJ ZK ZL ZM FT FU FV MP MQ MR SF SG SH YM YN YO EW EX EY LD LE LF RR RS RT XA XB XC DO DP DQ KU KV KW

12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9

1955 1956 1956 1956 1956 1956 1956 1956 1956 1956 1956 1956 1956 1957 1957 1957 1957 1957 1957 1957 1957 1957 1957 1957 1957 1958 1958 1958 1958 1958 1958 1958 1958 1958 1958 1958 1958 1959 1959 1959 1959 1959 1959 1959 1959 1959 1959 1959 1959 1960 1960 1960 1960 1960 1960 1960 1960 1960

87

QJ QK QL WE WF WG CS CT CU JH JJ JK PN PO PP VK VL VM BB BD BF HQ HR HS OD OE OF UA UB UC AM AN AO GR GS GT NU NV NW TD TE TF ZX ZY ZZ FA FB FC SJ SK SL YP YQ YR EG EH EJ LS

10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7

1960 1960 1960 1961 1961 1961 1961 1961 1961 1961 1961 1961 1961 1961 1961 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 1963 1963 1963 1963 1963 1963 1963 1963 1963 1963 1963 1963 1964 1964 1964 1964 1964 1964 1964 1964 1964 1964 1964 1964 1965 1965 1965 1965 1965 1965 1965

88

LT LU RN RO RP DW DX DY XD XE XF KR KS KT QA QB QC XU XV XW AJ AK AL MX MY MZ TA TB TC BM BN BO KD KE KF YG YH YJ OU OV OW FE FF FG RK RL RM SM SN SO GG GH GJ ZA ZB ZC QX QY

8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5

1965 1965 1965 1965 1965 1966 1966 1966 1966 1966 1966 1966 1966 1966 1966 1966 1966 1967 1967 1967 1967 1967 1967 1967 1967 1967 1967 1967 1967 1968 1968 1968 1968 1968 1968 1968 1968 1968 1968 1968 1968 1969 1969 1969 1969 1969 1969 1969 1969 1969 1969 1969 1969 1970 1970 1970 1970 1970

89

QZ DG DH DJ NR NS NT JD JE JF UL UM UN EA EB EC WU WV WW AX AY AZ NA NC NE HK HL HM RA RB RC MJ MK ML VG VH VJ TN TO TP GU GV GW CA CB CC FW FX FY XQ XR XS UD UE UF QM QN QO

6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3

1970 1970 1970 1970 1970 1970 1970 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1972 1972 1972 1972 1972 1972 1972 1972 1972 1972 1972 1972 1973 1973 1973 1973 1973 1973 1973 1973 1973 1973 1973 1973 197 4 1974 1974 1974 1974 1974 1974 1974 1974 1974 1974 1974 1975 1975 1975

90

BG BH BJ ZU ZV ZW JX JY JZ SP SQ SR LK LL LM PE PF PG DA DB DC NG NH NI BX BY BZ MM MN MO IR IS IT KA KB KC WL WM WN RG RH RI TK TL TM ED EE EF IU IV IW LX LY LZ GO GP GQ XJ

4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1

1975 1975 1975 1975 1975 1975 1975 1975 1975 1976 1976 1976 1976 1976 1976 1976 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 1977 1977 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1978 1978 1978 1978 1978 1978 1978 1979 1979 1979 1979 1979 1979 1979 1979 1979 1979 1979 1979 1980 91

XK XL OA OB OC UV UW UX QD QE QF CX CY CZ ZG ZH ZI JU JV JW VQ VR VS NM NN NO UG UH UJ IG IH IJ MA MB MC YS YT YU HN HO HP DD DE DF KX KY KZ IL IM IN BP BQ BR HW HX HY FM FN

2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11

1980 1980 1980 1980 1980 1980 1980 1980 1980 1980 1980 1981 1981 1981 1981 1981 1981 1981 1981 1981 1981 1981 1981 1982 1982 1982 1982 1982 1982 1982 1982 198 2 1982 1982 1982 1983 1983 1983 1983 1983 1983 1983 1983 1983 1983 1983 1983 1984 1984 1984 1984 1984 1984 1984 1984 1984 1984 1984

92

FO GD GE GF JR JS JT KO KP KQ LA LB LC MG MH MI PX PY PZ WR WS WT ZO ZP ZQ

12 -

1984

-

93

Tabell 3

Te s la – produc tion CODES . Data fro m 1947 to e nd.

Code

Month

Year

Code

h

Year

Cod Mont Cod e h Year e Month Year

FD

1

1947

BT

1

1951

QU

1

1955 YM

1

FH

2

1947

BU

2

1951

QV

2

1955 YN

FL

3

1947

BV

3

1951

QW

3

DR

4

1947

FP

4

1951

UO

DS

5

1947

FQ

5

1951

DT

6

1947

FR

6

AA

7

1947

KL

AF

8

1947

AH

9

GL

Mont

Code

Month

Year

1959

UA

1

1963

2

1959

UB

2

1963

1955 YO

3

1959

UC

3

1963

4

1955 EW

4

1959

AM

4

1963

UP

5

1955

EX

5

1959

AN

5

1963

1951

UQ

6

1955

EY

6

1959

AO

6

1963

7

1951

YA

7

1955

LD

7

1959

GR

7

1963

KM

8

1951

YB

8

1955

LE

8

1959

GS

8

1963

1947

KN

9

1951

YC

9

1955

LF

9

1959

GT

9

1963

10

194 7

OG

10

1951

CK

10

1955

RR

10

1959

NU

10

1963

GM

11

1947

OH

11

1951

CL

11

1955

RS

11

1959

NV

11

1963

GN

12

1947

OJ

12

1951

CM

12

1955

RT

12

1959

NW

12

1963

IA

1

1948

SC

1

1952

HT

1

1956 XA

1

1960

TD

1

1964

IB

2

1948

SD

2

1952

HU

2

1956

XB

2

1960

TE

2

1964

IC

3

1948

SE

3

1952

HV

3

1956

XC

3

1960

TF

3

1964

KH

4

1948

GX

4

1952

LG

4

1956 DO

4

1960

ZX

4

1964

KJ

5

1948

GY

5

1952

LH

5

1956

DP

5

1960

ZY

5

1964

KK

6

1948

GZ

6

1952

LJ

6

1956 DQ

6

1960

ZZ

6

1964

PB

7

1948

AU

7

1952

ZD

7

1956 KU

7

1960

FA

7

1964

PC

8

1948

AV

8

1952

ZE

8

1956 KV

8

1960

FB

8

1964

PD

9

1948

AW

9

1952

ZF

9

1956 KW

9

1960

FC

9

1964

NB

10

1948

ER

10

1952

TW

10

1956

QJ

10

1960

SJ

10

1964

ND NF

11 12

1948 1948

ES ET

11 12

1952 1952

TX

11 12

1956 QK 1956 QL

11 12

1960 1960

SK SL

11 12

1964 1964

TY

94

BA

1

1949

JN

1

1953

AB

1

1957 WE

1

1961

YP

1

1965

BC

2

1949

JO

2

1953

AC

2

1957 WF

2

1961

YQ

2

1965

BE

3

1949

JP

3

1953

AD

3

1957 WG

3

1961

YR

3

1965

HF

4

1949

NJ

4

1953

GA

4

1957

CS

4

1961

EG

4

1965

HG

5

1949

NK

5

1953

GB

5

1957

CT

5

1961

EH

5

1965

HJ

6

1949

NL

6

1953

GC

6

1957 CU

6

1961

EJ

6

1965

EK

7

1949

RD

7

1953

NX

7

1957

JH

7

1961

LS

7

1965

EM

8

1949

RE

8

1953

NY

8

1957

JJ

8

1961

LT

8

1965

EO

9

1949

RF

9

1953

NZ

9

1957

JK

9

1961

LU

9

1965

LP

10

1949

VA

10

1953

TG

10

1957

PN

10

1961

RN

10

1965

LQ

11

1949

VB

11

1953

TH

11

1957

PO

11

1961

RO

11

1965

LW

12

1949

VC

12

1953

TJ

12

1957

PP

12

1961

RP

12

1965

CE

1

1950

ZR

1

1954

ZK

1

1958 VK

1

1962

DW

1

1966

CG

2

1950

ZS

2

1954

ZL

2

1958

VL

2

1962

DX

2

1966

CO

3

1950

ZT

3

1954

ZM

3

1958 VM

3

1962

DY

3

1966

OP

4

1950

DL

4

1954

FT

4

1958

BB

4

1962

XD

4

1966

OR

5

1950

DM

5

1954

FU

5

1958 BD

5

1962

XE

5

1966

OS

6

1950

DN

6

1954

FV

6

1958

BF

6

1962

XF

6

1966

MT

7

1950

SX

7

1954

MP

7

1958 HQ

7

1962

KR

7

1966

MU

8

1950

SY

8

1954

MQ

8

1958 HR

8

1962

KS

8

1966

MV

9

1950

SZ

9

1954

MR

9

1958

HS

9

1962

KT

9

1966

VX

10

1950

MD

10

1954

SF

10

1958 OD

10

1962

QA

10

1966

VY

11

1950

ME

11

1954

SG

11

1958

OE

11

1962

QB

11

1966

VZ

12

1950

MF

12

1954

SH

12

1958

OF

12

1962

QC

12

1966

Code

Month

Year

Code

str. 2 Month

Year

Code Mont Year Cod Mont Year Cod Month Year

95

h

e

h

e

XU

1

1967

JD

1

1971

QM

1

1975

ED

1

1979

YS

1

1983

XV

2

1967

JE

2

1971

QN

2

1975

EE

2

1979

YT

2

1983

XW

3

1967

JF

3

1971

QO

3

1975

EF

3

1979

YU

3

1983

AJ

4

1967

UL

4

1971

BG

4

1975

IU

4

1979

HN

4

1983

AK

5

1967

UM

5

1971

BH

5

1975

IV

5

1979

HO

5

1983

AL

6

1967

UN

6

1971

BJ

6

1975

IW

6

1979

HP

6

1983

MX

7

1967

EA

7

1971

ZU

7

1975

LX

7

1979

DD

7

1983

MY

8

1967

EB

8

1971

ZV

8

1975

LY

8

1979

DE

8

1983

MZ

9

1967

EC

9

1971

ZW

9

1975

LZ

9

1979

DF

9

1983

TA

10

1967

WU

10

1971

JX

10

1975 GO

10

1979

KX

10

1983

TB

11

1967

WV

11

1971

JY

11

1975

GP

11

1979

KY

11

1983

TC

12

1967

WW

12

1971

JZ

12

1975 GQ

12

1979

KZ

12

1983

BM

1

1968

AX

1

1972

SP

1

1976

XJ

1

1980

IL

1

1984

BN

2

1968

AY

2

1972

SQ

2

1976 XK

2

1980

IM

2

1984

BO

3

1968

AZ

3

1972

SR

3

1976

XL

3

1980

IN

3

1984

KD

4

1968

NA

4

1972

LK

4

1976 OA

4

1980

BP

4

1984

KE

5

1968

NC

5

1972

LL

5

1976 OB

5

1980

BQ

5

1984

KF

6

1968

NE

6

1972

LM

6

1976 OC

6

1980

BR

6

1984

YG

7

1968

HK

7

1972

PE

7

1976 UV

7

1980

HW

7

1984

YH

8

1968

HL

8

1972

PF

8

1976 UW

8

1980

HX

8

1984

YJ

9

1968

HM

9

1972

PG

9

1976 UX

9

1980

HY

9

1984

OU

10

1968

RA

10

1972

DA

10

1976 QD

10

1980

FM

10

1984

OV

11

1968

RB

11

1972

DB

11

197 6 QE

11

1980

FN

11

1984

OW

12

1968

RC

12

1972

DC

12

1976

QF

12

1980

FO

12

1984

ANVÄNDS KODER FE

1

1969

MJ

1

1973

NG

1

1977

CX

1

1981

96

FF

2

1969

MK

2

1973

NH

2

1977 CY

2

1981

GD

-

-

FG

3

1969

ML

3

1973

NI

3

1977

CZ

3

1981

GE

-

-

RK

4

1969

VG

4

1973

BX

4

1977

ZG

4

1981

GF

-

-

RL

5

1969

VH

5

1973

BY

5

1977

ZH

5

1981

JR

-

-

RM

6

1969

VJ

6

1973

BZ

6

1977

ZI

6

1981

JS

-

-

SM

7

1969

TN

7

1973

MM

7

1977

JU

7

1981

JT

-

-

SN

8

1969

TO

8

1973

MN

8

1977

JV

8

1981

KO

-

-

SO

9

1969

TP

9

1973

MO

9

1977

JW

9

1981

KP

-

-

GG

10

1969

GU

10

1973

IR

10

1977 VQ

10

1981

KQ

-

-

GH

11

1969

GV

11

1973

IS

11

1977 VR

11

1981

LA

-

-

GJ

12

1969

GW

12

1973

IT

12

1977

VS

12

1981

LB

-

-

LC

-

-

ZA

1

1970

CA

1

1974

KA

1

1978 NM

1

1982

MG

-

-

ZB

2

1970

CB

2

1974

KB

2

1978 NN

2

1982

MH

-

-

ZC

3

1970

CC

3

1974

KC

3

1978 NO

3

1982

MI

-

-

QX

4

1970

FW

4

1974

WL

4

1978 UG

4

1982

PX

-

-

QY

5

1970

FX

5

1974

WM

5

1978 UH

5

1982

PY

-

-

QZ

6

1970

FY

6

1974

WN

6

1978

UJ

6

1982

PZ

-

-

DG

7

1970

XQ

7

1974

RG

7

1978

IG

7

1982

WR

-

-

DH

8

1970

XR

8

1974

RH

8

1978

IH

8

1982

WS

-

-

DJ

9

1970

XS

9

1974

RI

9

1978

IJ

9

1982

WT

-

-

NR

10

1970

UD

10

1974

TK

10

1978 MA

10

1982

ZO

-

-

NS

11

1970

UE

11

1974

TL

11

1978 MB

11

1982

ZP

-

-

NT

12

1970

UF

12

1974

TM

12

1978 MC

12

1982

ZQ

-

-

From 1984 have introduced , including the use of common code RVHP countries, according to ST SEV 2745-80

Month

Year 97

1984 1985 1986 1987 1988 1989 1990 1991 Datov媒 k贸d

1 2 3 4 5 6 7 8 9 10 11 12

S1 S2 S3 S4 S5 S6 S7 S8 S9 SO SN SD

T1 T2 T3 T4 T5 T6 T7 T8 T9 TO TN TD

U1 U2 U3 U4 U5 U6 U7 U8 U9 UO UN UD

V1 V2 V3 V4 V5 V6 V7 V8 V9 VO VN VD

W1 W2 W3 W4 W5 W6 W7 W8 W9 WO WN WD

X1 X2 X3 X4 X5 X6 X7 X8 X9 XO XN XD

A1 A2 A3 A4 A5 A6 A7 A8 A9 AO AN AD

B1 B2 B3 B4 B5 B6 B7 B8 B9 BO BN BD

For the year 1984, marking the production of data is planned under NT in 1021, but was held under the new labeling standards.

During the months October, November and December, while the corresponding figure in the second number, replacing the first letter Month namee name in English: October, November and December

ND

11

1948

ES

11

1952

TX

11

1956

QK

11

1960

SK

11

1964

NF

12

1948

ET

12

1952

TY

12

1956

QL

12

1960

SL

12

1964

BA

1

1949

JN

1

1953

AB

1

1957

WE

1

1961

YP

1

1965

BC

2

1949

JO

2

1953

AC

2

1957

WF

2

1961

YQ

2

1965

BE

3

1949

JP

3

1953

AD

3

1957

WG

3

1961

YR

3

1965

HF

4

1949

NJ

4

1953

GA

4

1957

CS

4

1961

EG

4

1965

HG

5

1949

NK

5

1953

GB

5

1957

CT

5

1961

EH

5

1965

HJ

6

1949

NL

6

1953

GC

6

1957

CU

6

1961

EJ

6

1965

EK

7

1949

RD

7

1953

NX

7

1957

JH

7

1961

LS

7

1965

EM

8

1949

RE

8

1953

NY

8

1957

JJ

8

1961

LT

8

1965

EO

9

1949

RF

9

1953

NZ

9

1957

JK

9

1961

LU

9

1965

LP

10

1949

VA

10

1953

TG

10

1957

PN

10

1961

RN

10

1965

LQ

11

1949

VB

11

1953

TH

11

1957

PO

11

1961

RO

11

1965

LW

12

1949

VC

12

1953

TJ

12

1957

PP

12

1961

RP

12

1965

CE

1

1950

ZR

1

1954

ZK

1

1958

VK

1

1962

DW

1

1966

98

CG

2

1950

ZS

2

1954

ZL

2

1958

VL

2

1962

DX

2

1966

CO

3

1950

ZT

3

1954

ZM

3

1958

VM

3

1962

DY

3

1966

OP

4

1950

DL

4

1954

FT

4

1958

BB

4

1962

XD

4

1966

OR

5

1950

DM

5

1954

FU

5

1958

BD

5

1962

XE

5

1966

OS

6

1950

DN

6

1954

FV

6

1958

BF

6

1962

XF

6

1966

MT

7

1950

SX

7

1954

MP

7

1958

HQ

7

1962

KR

7

1966

MU

8

195 0

SY

8

1954

MQ

8

1958

HR

8

1962

KS

8

1966

MV

9

1950

SZ

9

1954

MR

9

1958

HS

9

1962

KT

9

1966

VX

10

1950

MD

10

1954

SF

10

1958

OD

10

1962

QA

10

1966

VY

11

1950

ME

11

1954

SG

11

1958

OE

11

1962

QB

11

1966

VZ

12

1950

MF

12

1954

SH

12

1958

OF

12

1962

QC

12

1966

C O

M

C O

M

C O

M

C O

M

D

N T

D

N T

D

N T

D

N T

str. 2

E

O

Y E

A

H

r

XU

1

1967

XV

2

XW

E

O

Y E

A

H

r

JD

1

1971

1967

JE

2

3

1967

JF

AJ

4

1967

AK

5

AL

E

O

Y E

A

H

r

QM

1

1975

1971

QN

2

3

1971

QO

UL

4

1971

1967

UM

5

6

1967

UN

MX

7

1967

MY

8

MZ

E

O

Y E

A

H

r

ED

1

1979

1975

EE

2

3

1975

EF

BG

4

1975

1971

BH

5

6

1971

BJ

EA

7

1971

1967

EB

8

9

1967

EC

TA

10

1967

TB

11

TC

BM

C O

M

D

N T

E

O

Y E

A

H

r

YS

1

1983

1979

YT

2

1983

3

1979

YU

3

1983

IU

4

1979

HN

4

1983

1975

IV

5

1979

HO

5

1983

6

1975

IW

6

1979

HP

6

1983

ZU

7

1975

LX

7

1979

DD

7

1983

1971

ZV

8

1975

LY

8

1979

DE

8

1983

9

1971

ZW

9

1975

LZ

9

1979

DF

9

1983

WU

10

1971

JX

10

1975

GO

10

1979

KX

10

1983

1967

WV

11

1971

JY

11

1975

GP

11

1979

KY

11

1983

12

1967

WW

12

1971

JZ

12

1975

GQ

12

1979

KZ

12

1983

1

1968

AX

1

1972

SP

1

1976

XJ

1

1980

IL

1

1984

99

BN

2

1968

AY

2

1972

SQ

2

1976

XK

2

1980

IM

2

1984

BO

3

1968

AZ

3

1972

SR

3

1976

XL

3

1980

IN

3

1984

KD

4

1968

NA

4

1972

LK

4

1976

OA

4

1980

BP

4

1984

KE

5

1968

NC

5

1972

LL

5

1976

OB

5

1980

BQ

5

1984

KF

6

1968

NE

6

1972

LM

6

1976

OC

6

1980

BR

6

1984

YG

7

1968

HK

7

1972

PE

7

1976

UV

7

1980

HW

7

1984

YH

8

1968

HL

8

1972

PF

8

1976

UW

8

1980

HX

8

1984

YJ

9

1968

HM

9

1972

PG

9

1976

UX

9

1980

HY

9

1984

OU

10

1968

RA

10

1972

DA

10

1976

QD

10

1980

FM

10

1984

OV

11

1968

RB

11

1972

DB

11

1976

QE

11

1980

FN

11

1984

OW

12

1968

RC

12

1972

DC

12

1976

QF

12

1980

FO

12

1984

FE

1

1969

MJ

1

1973

NG

1

1977

CX

1

NEVYUŽITÉ 1981 KÓDY

FF

2

1969

MK

2

1973

NH

2

1977

CY

2

1981

GD

-

-

FG

3

1969

ML

3

1973

NI

3

1977

CZ

3

1981

GE

-

-

RK

4

1969

VG

4

1973

BX

4

1977

ZG

4

1981

GF

-

-

RL

5

1969

VH

5

1973

BY

5

1977

ZH

5

1981

JR

-

-

RM

6

1969

VJ

6

1973

BZ

6

1977

ZI

6

1981

JS

-

-

SM

7

1969

TN

7

1973

MM

7

1977

JU

7

1981

JT

-

-

SN

8

1969

TO

8

1973

MN

8

1977

JV

8

1981

KO

-

-

SO

9

1969

TP

9

1973

MO

9

1977

JW

9

1981

KP

-

-

GG

10

1969

GU

10

1973

IR

10

1977

VQ

10

1981

KQ

-

-

GH

11

1969

GV

11

1973

IS

11

1977

VR

11

1981

LA

-

-

GJ

12

1969

GW

12

1973

IT

12

1977

VS

12

1981

LB

-

-

LC

-

-

ZA

1

1970

CA

1

1974

KA

1

1978

NM

1

1982

MG

-

-

ZB

2

1970

CB

2

1974

KB

2

1978

NN

2

1982

MH

-

-

ZC QX

3 4

1970 1970

CC FW

3 4

1974 1974

KC

3 4

1978 1978

NO

3 4

1982 1982

MI

WL

-

-

UG

PX

100

QY

5

1970

FX

5

1974

WM

5

1978

UH

5

1982

PY

-

-

QZ

6

1970

FY

6

1974

WN

6

1978

UJ

6

1982

PZ

-

-

DG

7

1970

XQ

7

1974

RG

7

1978

IG

7

1982

WR

-

-

DH

8

1970

XR

8

1974

RH

8

1978

IH

8

1982

WS

-

-

DJ

9

1970

XS

9

1974

RI

9

1978

IJ

9

1982

WT

-

-

NR

10

1970

UD

10

1974

TK

10

1978

MA

10

1982

ZO

-

-

NS

11

1970

UE

11

1974

TL

11

1978

MB

11

1982

ZP

-

-

NT

12

1970

UF

12

1974

TM

12

1978

MC

12

1982

ZQ

-

-

101

Tabell 5 Signs of INFORMATION ON Tesla components - code with the date of manufacture.

Table contains data from January 1984 to December 1991.

From 1984 has been introduced, including the use of common code RVHP countries, according to ST SEV 2745-80 which replaced the previous standard Tesla NT 1021 (dvoumĂ­stĂ˝ letter code)

Year 1984 1985 1986 1987 1988 1989 1990

Month 1 2 3 4 5 6 7 8 9 10 11 12

S1 S2 S3 S4 S5 S6 S7 S8 S9 SO SN SD

T1 T2 T3 T4 T5 T6 T7 T8 T9 TO TN TD

U1 U2 U3 U4 U5 U6 U7 U8 U9 UO UN UD

Date code V1 W1 V2 W2 V3 W3 V4 W4 V5 W5 V6 W6 V7 W7 V8 W8 V9 W9 VO WO VN WN VD WD

X1 X2 X3 X4 X5 X6 X7 X8 X9 XO XN XD

A1 A2 A3 A4 A5 A6 A7 A8 A9 AO AN AD

1991

B1 B2 B3 B4 B5 B6 B7 B8 B9 BO BN BD

For the year 1984, marking the production of data is planned under NT in 1021, but was held under the new labeling standards.

During the months October, November and December, while the corresponding figure in the second number, replacing the first letter month names in English: October, November and December

.

102

Brimar Factory Codes Factory Codes http://myweb.tiscali.co.uk/g8hqp/audio/brimarcodes.html Some valve/tube manufacturers put a cryptic code on the glass, in addition to the normal valve type and logo etc.

The factory code is often etched into the glass, so may remain when the normal printing has been rubbed off. The codes used by Philips/Mullard/Valvo etc. are well documented on the web, but there is little information for the codes used by Brimar and other Thorn group brands (such as UK Mazda and later Ediswan).

I have gathered together some Brimar codes here. Some are gleaned from the web - I have tried to give correct attribution. Others are from my own collection - there seem to be lots of Mazda valves around on eBay in the UK at

present.

Anyo ne owning Brimar/Mazda valves will know that their factory codes tend to be harder to read than the Philips ones, and more easily smudged. In many cases the code is less resilient than the normal printing, but there will be times when the code may be the only way of identifying the valve type so a list will hopefully be useful.

Structure of Brimar Codes The suggestion given here is not my own, but gleaned from the Vintage Amps bulletin board - see the Wed Mar 07, 2007 9.08am post by saros141. A Brimar code consists of two parts. The first part is three characters, number-letternumber, which give the date of manufacture. The last number is the last digit of the year (so this suffers from the same ambiguity as the Philips code). The letter gives the month (A=January etc.), while the first number gives the week within the month. For example, 2C7 is the second week in March 1957 or 1967. However, I have a 6/30L2 (ECC804) which has a date code of 1N8 so are some letters omitted from the month code sequence, or is it more complicated than we think?

The second part is just a number, usually three or four digits long, which gives the valve type. Different versions of a particular valve type will have different numbers, although these may sometimes be grouped together. For example, 1573 and 1574 are types of ECC83 but so is 2162.

Between the two parts of the code there may be a slash /, or a space, or nothing at all. Sometimes it is difficult to distinguish a three-digit number preceded by a slash from a four-digit number with no separator, so there is some uncertainty in some of the four-digit codes starting with 1. For example, the code for ECC82 is said to be 1571 (see ref AA1), but I have some which are clearly marked 571. However, I have some 19AQ5 marked 660, and others marked 1660, so perhaps xyz and 1xyz are sometimes related? Digits 5 and 8 can look quite similar. The code may be horizontal or vertical, and could occur at almost any height on the glass envelope. Sometimes it will be obscured by the normal printing.

Brimar Codes Ref Code DPK 195 DPK 229 DPK 244 VA1

422

DPK DPK DPK DPK DPK

524 557 571 585 660

DPK 977 1175 or 175?

DPK 1224 DPK 1234 DPK 1252

Eu US Other EBC90 6AT6 DH77 EK90 6BE6 X727 6BR7 CV2135 6V6GT CV511 Y 9BW6 12AH8 ECC82 12AU7 CV491 12BH7?

HL90 19AQ5 12AX7 E83CC CV4004, 6057 WA

DPK

Notes

see 8979

see also 1571 valve is unmarked but looks internally like a 12BH7 150mA version of EL90/6AQ5, see also 1660 box anode, black, 1 flange, D getter - see 3977

6AK6 EF93 EF90

6BA6 6BH6 6BW6

see 6224 see 3981 103

DPK 1274 DPK 1291 DPK 1294 1426 or DPK 426?

VA1 1432 VA1 1565 AA1

1571

DPK, 1573 VA1 DPK, 1574 VA1 1576 or DPK 1876?

DPK 1660 DPK 1676 DPK 1681 DPK 1682 DPK 1686 DPK 1687 DPK 1791 DPK, VA1 DPK DPK, VA1 DPK, VA1 DPK, JR1 DPK

EL821 6CH6 CV2127?

PF818/E 7ED7/6 30F5/6F23 F812 EL7 EE80 6F28 EZ90

30F5 and 6F23 are very similar, was one a mislabelling?

6X4 6X5GT

ECC81 12AT7 ECC82 12AU7

CV491, CV4003, 13D4, 13D5, 13D8

see also 571

ECC83 12AX7 CV4004

half-boxed- plate

ECC83 12AX7

14mm plate

ECC804 6GA8

6/30L2

HL90 19AQ5 PCE800 9GB8 PCC805 7EK7 PCC806 PCL801 PCL800 16GK8

30FL2 30L15 30L17 30PL1 30PL13

I only have one of these; looks identical to 2195 version.

150mA version of EL90/6AQ5, see also 660

ECL82 6BM8 6PL12

pentode anode grey, staples facing out, no grid tabs, see 2242

1796

EL84

6BQ5

1822

PL84

15CW5

2160

ECC81 12AT7

black wing anode with rounded end

2162

ECC83 12AX7 CV4004

14mm plate

2167

ECC88 6DJ8

see also 3910

2195

ECC804 6GA8

300mA version of EL86

6/30L2

DPK 2242

ECL82 6BM8 6PL12

DPK DPK DPK DPK

PC97 4FY5 PCC84 7AN7 30L1 PCF80 9A8 30C1 PCL84 15DQ8

2510 2520 2540 2562 2563 or DPK 2568?

DPK 2701 TC1 3876 JR1 3910 VA1, 3977

DPK DPK 3980 DPK 3981

DPK 3982?

3986 or 3988?

VA1 3987 DPK 6224

DPK

see 3986

most of my ECC804 have this code pentode anode black, staples facing in, grey heat tabs on control grid posts, see 1791

30PL15

KY80

2J2 5965 ECC88 6DJ8

U26 see also 2167

ECC83 12AX7 CV4004, 6057

box anode, grey, 1 flange, O getter - see 977

ECC81 12AT7 CV4024

SQ version, black single-flange anode with square end black anode, round getter, double support (see 1252)

6BW6 QV03/1

2

6062

EL821 6CH6

CV4039, SQ 5763 CV4055

ECC82 12AU7 CV4003 EF93 6BA6 CV454

see 1274

17mm plate see 1224 104

Russian tubes eq.

105

106

107

108

I n f o rm a t io n B e f o re U s in g o ld v a c u u m t u b e s Older designs, using glass as an insulatin medium,do tend to leak gas over time. It is not the glass that is porous to gas, but the �Ko v a r � alloy used to seal the glass to metal parts in the tube. Kovar is also subject to rusting when moisture is present. Such devices should be kept in a sealed plastic bag in storage and rotated through the equipment at least once every twelve months. Physically, the larger the tub, more surface area of Kovar, and the greater the possibility of gassing up.

D e g a s s in g Tubes that may have gaussed up can be partially degassed by putting them in the equipment and running them for several hours with filament voltage only applied.

After the initial filament-only degassing; operation for an hour or so at reduced plate and screen voltages is desirable. This allows the getter to soak up and hold any residual gasses.

BE CAUTIOUS AND HAVE FUN WHEN WHEN YOU WORKING WITH AND DECODES VACUUM TUBES

109