How did they come up with Vacuum Tube numbers/letters

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I was trying to find something about this on google and found little.
Do the numbers and letters on tubes actually mean anything?

Yes, I know the FIRST digit is the filament voltage
6L6 would be 6.3 volts 12AU7 = 12 volts, 5U4 = 5 volts
35L6G = 35 volts

Ok, but do the numbers and letters after the first have any meaning?

For example, "6SN7".
A 6SN7 tube is listed as a "dual triode"

It has a 6 volt filament, but what does the SN7 mean?


One other thing, what is a "heptode"?
(another term i found but didn't find any definition)

Thanks

 

[Rich Grise]

I was trying to find something about this on google and found little.
Do the numbers and letters on tubes actually mean anything?

Yes, I know the FIRST digit is the filament voltage
6L6 would be 6.3 volts 12AU7 = 12 volts, 5U4 = 5 volts
35L6G = 35 volts

Ok, but do the numbers and letters after the first have any meaning?

For example, "6SN7".
A 6SN7 tube is listed as a "dual triode"

It has a 6 volt filament, but what does the SN7 mean?

The 7 has to do with the number of electrodes - in this case, one heater,
two cathodes, two grids and two plates.

The letters are basically picked out of thin air. =:-O

One other thing, what is a "heptode"?

Seven electrodes, AKA "pentagrid converter" - it's a local oscillator and
mixer all in one.

(another term i found but didn't find any definition)

Didn't look very hard:
http://www.google.com/search?hl=en&source=hp&q=define:heptode

Hope This Helps!
Rich

 

[Spurious Response]

I was trying to find something about this on google and found little.
Do the numbers and letters on tubes actually mean anything?

Yes, I know the FIRST digit is the filament voltage
6L6 would be 6.3 volts 12AU7 = 12 volts, 5U4 = 5 volts
35L6G = 35 volts

Ok, but do the numbers and letters after the first have any meaning?

For example, "6SN7".
A 6SN7 tube is listed as a "dual triode"

It has a 6 volt filament, but what does the SN7 mean?


One other thing, what is a "heptode"?
(another term i found but didn't find any definition)

Thanks

http://www.duncanamps.com/technical/tubenumber.html#USA (RETMA) system

 

[TTman]

http://www.duncanamps.com/technical/tubenumber.html#USA (RETMA) system

LOL most interesting read I've had in a long time

 

[TheGlimmerMan]

..i was referring to the filament voltage.

The page I posted a link to covers it entirely.

 

[Tim Williams]

Confused a bit by metal tube nomenclature, where the can (the shield)
was grounded through a pin, which was counted as an electron -- so a
6SK7 is a pentode with heater, cathode, three grids, plate, and shield.

So the 6V6 is a beam tetrode (heater, cathode, two grids, plate and
shield), while the 6AQ5 is the _exact same innards_ put into a glass
envelope, with the loss of the shield 'electrode'.

I don't think that's it. 6V6 has no shield, nor a need of one. The EIA
basing diagram 7AC shows pin 1 is "S/NC", which I've never seen used as
anything but a tie point. The pin is usually missing from the tube base.

I guess octals often had plus one. Example: 6X4, a dual indirectly heated
power rectifier for radios. 7 pin miniature. The octal was 6X5. Or 6C4,
which is a lone 12AU7 triode in 7 pin mini. Octal 6C5.

I read somewhere that the designer was often free to pick unclaimed
letter pairs, so initials would sometimes creep in there. Where it made
marketing sense (for instance the whole '6S' line of metal-can octal pin
tubes with special shielded bases) the company involved would push a
system.

Supposedly, the letters were assigned more-or-less sequentially. As you
go through TV history, you'll see deflection tubes like 6BG6, then 6BQ6,
then 6DQ6, then 6LZ6, then...

Rectifiers seem to go the opposite direction sometimes. There's a bunch
towards the alphabetical end of the series, like 6X4, 5Y3, 1X2, etc. But
there's also 3A3, 6AX4, etc.

There were also numbered designations (e.g., 7199), which I don't know if
they had any rules at all. I wouldn't be surprised if ranges were
reserved by manufacturers, or by series.

Finally, a new system was invented, the electrode number - letter type -
identifier number scheme, from which we have tubes like 2C53 and 2E26, and
semiconductors like 1N60, 2N3904 and 4N25.

Tim

 

[Rich Grise]

So, do you know for sure that the early references that I'm going on
were incorrect about the _inside part_ of the tubes being the same?

Cheers!
Rich

 

[Baron]

Rich Grise Inscribed thus:

Cheers!
Rich

Great video ! I've seen it used as a teaching aid as well !