Numbering/lettering of tubes (USA type).

I don't have an answer to your question. However, note that any significant numbering scheme always falls apart as technical progress advances faster than letters and numbers can be contrived to match. For example, we started with 1Nxxxx = Diode, 2Nxxxx = Triode (BJT, FET), 3Nxxxx = (Dual gate MOSFET), 4N = Optoisolator, etc. That lasted about 10 years before devices arrived that could not easily be crammed into the significant numbering scheme. The JEDEC would have been better off just starting at 00001 and counting up in sequence. It would seem that the semiconductor people had not learned the lessons of tube numbering, and repeated the basic mistakes.

The IB3 is easy. The IB3, 3A3, 2AV2 etc. are all HV rectifiers, and the fi laments were designed to run off parasitic windings of the HV transformers. The less turns the better I guess. The 1B3 was for B&W TVs, the 3A3 for color TVs which, not coincidentally, had about twice the HV as the B&W vers ions, so a turn or so around the core would give the correct voltage.

Tubes like the 800 series or the early 4 pin radio tubes were never part of the standard numbering scheme, and as for the others, if you consider the many thousands of tubes from dozens of manufacturers that were pigeon-holed into the handful of basic types, you'd need unique letters just to identif y them.

The 6.3V heater chain used by other tubes cannot be used as a 26kV insulation barrier would stop all heat getting to the cathode. So the tube cathode is directly heated by a winding that floats at the HT voltage.

Since the load current is 50mA max, a low powered heater is enough - 1.25V and 200ma do the job.

The 1.25V needed is conveniently derived by a single turn around the HOT core, carried out with wire insulted to stand 20kV or more.

.... Phil

The heater winding needed very thick insulation, so it made sense to use fewer turns with more copper.

The 2N numbering system was from JEDEC, the US Joint Electron Device Engineering (council, command, committee, conspiracy, C-something, anyway). See e.g. .

You might look at

Cheers

Phil Hobbs

I agree with you here.

I don't agree they would be better off. The system was valuable for many early tubes and I didn't expect it to work forever. so I ignored it when it didn't work. Numbers in sequence would have meant nothing,

OTOH, the relationship between a 6SD6 and a 12SD6 is clear. (I'm not positive those exact tubes existed. It's been a long time.)

And the tubes in my father's battery powered tube radio, with names like

Someone, maybe my father, also bought a crystal radio, a 3-inch diameter, 3/4" brown plastic box with holes in one side to listen through, and a green wire with an alligator clip coming out of it. It had a clear plastic rounded fluted tuning knob and only got one station in Indianapolis, the strongest one I think. But one is enough, if we'd ever been without power during an emergency. But I dont' think we ever were.

As to 813 etc. I haven't found any all numerica names but I wouldn't have thought the 8 referred to voltage. That I would have taken as some subset of sequential numeric naming.

I suspect the very early tubes were simply numbered in order of development. My old Radiola uses an 80, a 171 and a bunch of 27s. The 27s are 2.5v filaments and the 171 and 80 are 5v.

In short, there is no "standard" numbering scheme for American vacuum tubes.

In the "beginning" numbers 01 though 99 were assigned pretty much on a "first come first serve" basis. More confusing were, for example, adding a number to signify manufacturer. For example, the type 27. 127, 227, 327, 427 etc were the same tube but by different manufacturers.

Starting in the '30s, they got together and agreed that the first number would be the filament voltage.

An original "idea" of assigning 1 or 2 letters in the middle on a per function basis went to Hell surprisingly fast.

During WWII, the military also came up with VT-nnn numbers that referenced "normal" tubes, such a 27, 80, 6SK7 etc.

Transmitting tubes were different, usually "high numbers" such as the 807, 811, 813, 1625 and so forth.

Then there's the entire gambit of 4-digit "industrial" types. Nominally in the 4000-9000 range.

The only other thing they agreed on was keeping the type the same across different filament voltages. 6BE6 and 12BE6 as an example.

Then of course, a few manufactures came up with their own bastard numbers. Like Taylor TZ-40. "Taylor, Zero bias, 40 watts."

As with all things they start off with a sysem and as new items are developed that system falls apart. I think tubes were numbered in order to start with. Then they were listed as the first number being the filiment voltage, letters to indicate what type and the last number the number of elements.

Some power tubes started with a number a dash and another several numbers such as a 3-500. That was the number of elements and the plate dissaplation. A 4x150 started the same way. Later it was a 4cx150 that indicated a ceramic seal instead of glass. Then a letter was added to the end to indicate the filiment voltage.

Simiconductors tried the same system. First number the number of junctions. Not sure about the N and the last numbers were just assigned in order. Later some even had dots of colored paint on them This was for the range of gain on them.

Japan tried the same thing with the numbers. One was the number of junctions. leters for the type, RF , AF. Many of them left off the starting 2 on them and yu just had to remember to add that when looking at them.

My 1933 RCA/Cunningham Radio Tube Manual agrees. Pg 143:

-------------------------------------------------------------- THE NEW TUBE-NUMBERING SYSTEM

Type numbers for new tubes are now being assigned in accordance with the new system adopted in the early part of 1933 by the Radio Manufacturers Association. A new system was required because practically all of the available two and three digit numbers have been utilized.

... (description of the numbering system, as described above)

While these rules assist to some extent in classifying tubes by filament voltage and function, the significance of the individual symbols will in most cases be inadequate to identify the specific features of a tube.

--------------------------------------------------------------------

I love old manuals!

John :-#)#

The 813 is an industrial tube, not a consumer numbered tube.

God you are old.

Then something must be wrong. Nobody ever agrees with me.

Exactly. The whole idea is that they are meaningless so that advances in tube technology would not be lost in a jumble of letters and place holders. It didn't take long for all the tube numbering systems to fall apart. The first problem was when manufacturers started putting two different tubes in one glass or metal envelope. For example, the

The next to go was the Compactron with multiple devices inside the envelope and more pins on the base. The habit of significant numbering was maintained, so they too had numbers that were difficult to decode. Some Compactrons ended in "11" for a triple triode where two triodes shared a common cathode. No way to deduce the internal structure with just the total number of elements:

I think the final change to non-registered numbering was the Nuvistor: Some Nuvistors used the significant numbering scheme (6CW4, 6DS4, etc) while others used non-significant 4 digit numbers (7586, 8056, etc) depending on what the target market wanted.

The old adage "Those who don't remember the screwups of the past, are condemned to repeat them" is quite true. However, the problem isn't that they don't remember, it's that they never experienced the problem. I've worked for or with 3 companies all of whom had significant numbering systems fall apart on them. Renumbering a companies entire product option system and internal part numbering system, is not a trivial or painless exercise. Each company had it's own "better" idea, which eventually failed (usually after the perpetrators were long gone).

Oddly, some of these numbering failures creating an even bigger problem, where individual departments each contrived their own numbering scheme. This problem is fairly common in the consumer level computer business. Marketing would have a clever name for the product, engineering would have a code name, production would have it's own product number, and sales would build a catalog of short and simplified numbers that could be easily remembered by customers. While immensely confusing to the typical customer, it does have some organizational benefits for the manufacturer.

Unfortunately, I was partly responsible for creating a significant product numbering scheme at a former employer. It took about 8 years for the system to fall apart, which is about typical. Adding a few extra digits required 2 years of rewriting every computer program that the company was using. A few years later, the company went out of business, just before they again ran out of significant digits.