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 Post subject: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 7:11 pm 
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Just wondering what it means...thanks

Kenny KE4HVE


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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 7:50 pm 
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It kinda means the number of elements. A letter can mean a variation of some sort, neither are hard and fast rules but always good for a guess as to what is going on.

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 7:59 pm 
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I believe it was supposed to be the number of active elements to the pins, though it does seem to vary at times.

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 10:08 pm 
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+1
But this doesn't apply to the older standard base two digit tubes like an 80 or 77. Miniatures, octal, and loctals generally follow that rule but there are exceptions like a 6C4 and 6J5 both have the same # of elements.

Terry N3GTE


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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 10:23 pm 
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Yep it is generally means the number of elements in a tube.

6AU6 Cathode, 3 grids, plate, filament (6)
5Y3 Two plates, a filament (3)

But sometimes it doesn't :?

35Z5 Plate, 2 filaments, cathode (4)
But note there is a 35Z4 tube as well which is different - Plate, 1 filament, 1 cathode (3) ???

The best laid plans of mice and men?

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Last edited by Eickerman on Jan Thu 11, 2018 10:35 pm, edited 3 times in total.

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 10:29 pm 
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With older tubes, the last number is-----the last number.

With newer tubes, the last number might be the number of elements----or it might not....;)

When you master the US system, tell us about European tubes......

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Thu 11, 2018 10:54 pm 
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Eickerman wrote:

The best laid plans of mice and men?

Curtis Eickerman


I used to think that quote was maybe from Shakespeare ... but I was wrong.
I'm glad I looked it up because I'm richer of mind now with yet another trivial fact.

"To a Mouse, on Turning Her Up in Her Nest With the Plough, November, 1785"
Robert Burns

The ..poor sad little mouse without a home now...
so he writes this poem to the little mouse he refers to as a "fellow mortal".

https://en.wikipedia.org/wiki/To_a_Mouse

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Fri 12, 2018 7:11 pm 
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Radioroslyn wrote:
+1
But this doesn't apply to the older standard base two digit tubes like an 80 or 77. Miniatures, octal, and loctals generally follow that rule but there are exceptions like a 6C4 and 6J5 both have the same # of elements.

Terry N3GTE

The 6J5 was originally a metal tube with pin 1 connected to the metal shell, which was used as a shield. Perhaps they counted that as an element. This does not account for all of the exceptions, put perhaps it accounts for some of them. Are there any cases where the last number is more than 1 too high?

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Fri 12, 2018 7:31 pm 
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35Z4 was first then a pilot lamp tap was added thus 35Z5.
I think sometimes the last number represents how many pins are used to use the tube to its best performance.
That is why you see some triodes that have and end number of 5 or 6.


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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Fri 12, 2018 8:01 pm 
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Here are a couple: 5Y3 and 5Y4. Same tubes just different pin out. 5U4 and 5V3. Only slightly different electrical spec. How about 35W4 and 35Z5? Only different size.

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Fri 12, 2018 8:13 pm 
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....And then there are the Locktals ... that, to me at least, make no sense.

They are the Locktal equivalent of other tubes... so why not use the same original tube designation plus an "L" in front or at the end, ...or some other designation for a base insertion version.?

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sat 13, 2018 1:53 am 
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I've always assumed people just were not as logical back in those days. Sure, the really smart ones who designed the concept of radio probably were extremely logical, but when the garage mechanic started modifying designs of the tubes to meet his needs, then all new "standards" were created that likely made no logical sense.

Today, everyone can see best practice examples and logical thinking by simply reading any number of thousands of books, or browsing the internet. So it comes more natural to more people today than it did in yesteryear.


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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sat 13, 2018 4:32 am 
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As already stated last number was SUPPOSED to be element count, in actual practice not always the case...

In addition to 35Z5 & 35W4 the Loktal 35Y4 is also identical... Also 35Z3 is Loktal equivalent of 35Z4...

Talking about AA5 typs 50L6 & 50C5 are equivalent anong with Loktal 50A5...

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sat 13, 2018 5:05 am 
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I was always taught that the last number in the EIA system was originally supposed to indicate the number of functional elements in the tube. But to promote better use of the alphabet, they also permitted the last number to indicate the minimum number of connections needed for the tube to function normally. This is the number of pins minus 1, since the heater or filament is only counted time (the return side of the circuit was presumed).

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sat 13, 2018 7:11 am 
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Greetings to the Forum:

Curtis writes:
Quote:
6AU6 Cathode, 3 grids, plate, filament (6)


In his example, it would appear that the heater is counted as an element.

But.... how about the 6EA8 or the 6GH8? These tubes are triode-pentode tubes, so 8 makes sense.... but only if you don't count the heater.

Seems to me that the element count standard isn't very.

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sat 13, 2018 10:36 am 
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From Mark "When you master the US system, tell us about European tubes......"

Just sorting out valves for a 1932 Brit supie radio coming my way.

Some of the ones used are:

AC/S2 with equivalents D4, MH4, HL4, MHL4, 41MHL, A30D

MHL4 with equivalents: AC/HL, 154V ,AC/PEN, MP/PEN, 7A2, KT42, PEN4VA, A70B, APP4A, N40, P4VA

Well I have a AC/HL and an AC/2HL close maybe, an AC2/PEN close maybe. Could go on but I wont. All these equivalents need a check of course and some maybe a 5 Pin base with a side screw terminal or a 7 Pin base.

Best to wait until I get the radio and test whats there before I start looking.

Lots of the radio manufacturers used the same valve (possibly made in the same factory) but gave it their own code).

It did get so much better after the International Octal although one valve maker didnt agree with it and brought out its own version the 8 pin Mazda Octal, No! not interchangeable mechanically with IO.

Gary


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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sat 13, 2018 1:16 pm 
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Quote:
But.... how about the 6EA8 or the 6GH8? These tubes are triode-pentode tubes, so 8 makes sense.... but only if you don't count the heater.


Those tubes are consistent if you go by the "functional connections" count. The cathode and G3 of the pentode section are tied together internally, along with the internal shield, to pin 7. Since there's no practical way for the user to separate them, they are only counted once. The heater, which is also counted once, then becomes the 8th item.

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 Post subject: Re: What does the last number on a tube mean???
PostPosted: Jan Sun 14, 2018 1:28 am 
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radios2100 wrote:
I've always assumed people just were not as logical back in those days. Sure, the really smart ones who designed the concept of radio probably were extremely logical, but when the garage mechanic started modifying designs of the tubes to meet his needs, then all new "standards" were created that likely made no logical sense.

Today, everyone can see best practice examples and logical thinking by simply reading any number of thousands of books, or browsing the internet. So it comes more natural to more people today than it did in yesteryear.
They were logical, just not far sighted enough (common problem even today). The 'system' seemed logical enough, in the beginning, but was quickly outstripped by the proliferation tubes with 'minor' differences.


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