Helps to press tab instead of return. Oh well

You know, now I know that 201A tubes have a thoriated tungsten filament, and that 201 tubes have a plain tungsten filament. What do all of the other tube numbers with an A at the end mean? There's 24A and 71A and 6AU6A, etc., etc., etc. What is it all about? Does this simply note an improvement to an otherwise identical tube?

Thomas

I know with the 201 tube its filament was rated at 1 amp and the 201A was rated at 250ma, there is a 201B and 201C and they both have lower filament currents as well and as my poor memory serves me I think the 201C had a filement current of .060 amp. I am sure this applied to all of the early tubes.
I was told by a old fellow that on the later tubes a letter after the basic part number indicated an improvement of some sort to the tube, ie, improved support structure.
Gregb

:Helps to press tab instead of return. Oh well
:
:You know, now I know that 201A tubes have a thoriated tungsten filament, and that 201 tubes have a plain tungsten filament. What do all of the other tube numbers with an A at the end mean? There's 24A and 71A and 6AU6A, etc., etc., etc. What is it all about? Does this simply note an improvement to an otherwise identical tube?
:
:Thomas

:Helps to press tab instead of return. Oh well
:
:You know, now I know that 201A tubes have a thoriated tungsten filament, and that 201 tubes have a plain tungsten filament. What do all of the other tube numbers with an A at the end mean? There's 24A and 71A and 6AU6A, etc., etc., etc. What is it all about? Does this simply note an improvement to an otherwise identical tube?
:
:Thomas

Hey Thomas,

One place for a little reading on the subject is http://www.rru.com/~meo/Guitar/Tubes/usa-des.html

Radiodoc

::Helps to press tab instead of return. Oh well
::
::You know, now I know that 201A tubes have a thoriated tungsten filament, and that 201 tubes have a plain tungsten filament. What do all of the other tube numbers with an A at the end mean? There's 24A and 71A and 6AU6A, etc., etc., etc. What is it all about? Does this simply note an improvement to an otherwise identical tube?
::

The 24A had an improved quick heating heater structure. the original UX-171 used a thoriated filament, as did the UX-112. The A versions of these tubes were equipped with oxide coated filaments. The 6AU6a featured an imoroved element structure with higher rated plate dissipation and lower interelectrode capacitance.
::Thomas
:
:Hey Thomas,
:
:One place for a little reading on the subject is http://www.rru.com/~meo/Guitar/Tubes/usa-des.html
:
:Radiodoc
:

You know, the Majestic 24 tubes which I recently purchased (I forgot their exact numbers 224, 324, whatever) take a terribly long time to heat up. They are pittiful! I understand this now because all of my 24As are much quicker to heat up.

Thomas

:You know, the Majestic 24 tubes which I recently purchased (I forgot their exact numbers 224, 324, whatever) take a terribly long time to heat up. They are pittiful! I understand this now because all of my 24As are much quicker to heat up.
:
:Thomas

If you think that the early Majestic G-24 tubes take a long time to heat up you should try a 1927 or 1928 vintage RCA UY-227! It can take up to three minutes for these babies to get hot enough to do their stuff!. Thet is the reason that the Blur, tipped Arcturus 127 detector tubes are so much more common than any of the other blue tubes. The 127 used a quick heating carbon filament heater, and would get up to tempertature in as little as 25 seconds. They are often found in the detector sockets of sets that are otherwise equipped entirely with Radiotrons.

How come the detector sockets? I love Arcturus tubes. Wish I had some blue ones. I'll have to get some someday.

What do they use in more modern tubes like the #57? They only take about 6 to 10 seconds to warm up.

T.