[mordy]

I have one pair of NU 76 in military JAN boxes dated 1945, and an earlier pair, date code F (?), but based on construction, from the late 1930's. They all sound about the same to my ears. The 76 was first introduced in 1934.

I put together a list of National Union date codes (can't remember where I got it from but maybe Antique Radio Forum, and I extrapolate from this list. NU stopped production in 1954 (bought by Sylvania).
First letter:
G 1943
H 1944
I 1945
J 1946
GU is July 1943
HU is June 1944
IN is May 1945
IU June 1945
IU April 45
IU March 45
HC Oct 44
Quarters?:
U is March April June/July May maybe
N is March April May probably
R June
C October?
Can't figure out the exact meaning of the second letter...
If someone has better information, please let me know.

 

[whirlwind]

I have the metal base VT-94. They are nice tubes.
mordy, your HC code seems to be correct.

 

[gibosi]

I put together a list of National Union date codes (can't remember where I got it from but maybe Antique Radio Forum, and I extrapolate from this list. NU stopped production in 1954 (bought by Sylvania).
First letter:
G 1943
H 1944
I 1945
J 1946
GU is July 1943
HU is June 1944
IN is May 1945
IU June 1945
IU April 45
IU March 45
HC Oct 44
Quarters?:
U is March April June/July May maybe
N is March April May probably
R June
C October?
Can't figure out the exact meaning of the second letter...
If someone has better information, please let me know.

I hadn't seen these codes before, so good job!

I have two JAN #76, and the box on one is dated. April, 1945, and the other is May, 1945, but both carry the same two-digit code, "IU". It may well be that these codes represent the "painting, packaging and shipping" dates and "U" indicates a multi-month period, but of course, I don't know.

The older #76, below to the right, has a single digit, "F" printed to the right of the main logo, and this single digit doesn't fit into the later two-letter dating scheme. Further, since it has an older construction, welded plates as opposed to riveted plates, taller bottle, and an older style top mica structure, I am inclined to think late 1930's, but of course, I can't know for sure.

 

[mordy]

I hadn't seen these codes before, so good job!

I have two JAN #76, and the box on one is dated. April, 1945, and the other is May, 1945, but both carry the same two-digit code, "IU". It may well be that these codes represent the "painting, packaging and shipping" dates and "U" indicates a multi-month period, but of course, I don't know.

The older #76, below to the right, has a single digit, "F" printed to the right of the main logo, and this single digit doesn't fit into the later two-letter dating scheme. Further, since it has an older construction, welded plates as opposed to riveted plates, taller bottle, and an older style top mica structure, I am inclined to think late 1930's, but of course, I can't know for sure.

It is also possible that I was able to compare the dates on some original boxes with the date codes on the tubes.
One of the mysteries that are left are the dating of Tung Sol tubes. Even though the dates on the tubes are supposedly warranty expiration dates, it still gives you an idea of the year of manufacture within a year or so.
Somewhere I have a small list of Tung Sol dates as they appear on the original boxes and on the tubes (the main problem is the strange letter combinations). I was wondering if, with the help of forum members, we could put together a list based on the boxes and the tubes. Personally, I feel that it would be helpful. In addition, I believe that many military tubes made by Tung Sol have the regular dates on the them, but tubes for civilian use have the letter codes, and it would be possible to put together pairs that way.
Here is a "matched pair" - identical construction. One is from the second week 1962 factory 3(?) and the other one from KK3:

 

[gibosi]

Those of you rolling 6J5, how do the RCA sound? I have a pair of RCA Type 76, manufactured in 1936, that sound awful good too.

 

[whirlwind]

When I first got these Arcturus, I thought they were RCA, but someone else here thought they were National Union.
They look a lot like your NU 76.
They are in my OTL now and sound great paired with Chatham 6AS7G




Not sure what this code is.

 

[Xcalibur255]

My vote would also be National Union.

 

[gibosi]

When I first got these Arcturus, I thought they were RCA, but someone else here thought they were National Union.
They look a lot like your NU 76.
They are in my OTL now and sound great paired with Chatham




Not sure what this code is.

I would agree. They look exactly like my NU 76, except yours has an octal base. And the code, SA, doesn't seem to be an NU code, and there's no telling what it might mean.

 

[mordy]

Found a video showing RCA tube manufacturing in Lancaster, PA.
Haven't seen this one before. What is striking to me is the almost total lack of automation - everything is made by hand. And the lack of safety precautions...
The unhurriedness of certain parts of the operation is also striking.
At 3:10 the soldering process of the pins is shown - that's the only quick thing in the film.
Although the date is given as 1966 something tells me that the film is from much earlier - don't know if anode cap tubes were being manufactured then. (The announcer actually states that 1966 is the date on the film reel itself)

 

[mordy]

Found a video showing RCA tube manufacturing in Lancaster, PA.
Haven't seen this one before. What is striking to me is the almost total lack of automation - everything is made by hand. And the lack of safety precautions...
The unhurriedness of certain parts of the operation is also striking.
At 3:10 the soldering process of the pins is shown - that's the only quick thing in the film.
Although the date is given as 1966 something tells me that the film is from much earlier - don't know if anode cap tubes were being manufactured then. (The announcer actually states that 1966 is the date on the film reel itself)

Read through the numerous comments - a couple of memorable ones:
Some of the best tubes were made by our grandmothers!
The fancy dresses and jewelry worn indicates that the workers were told that they were going to be filmed - they were not wearing regular work clothes.
"The land of lead and asbestos."

 

[triod750]

Although the date is given as 1966 something tells me that the film is from much earlier

Her hair says 1966...

 

[gibosi]

Her hair says 1966...

And her hair, jewelry and clothing also suggests the 1950's. So I agree with mordy.

Further, I worked in a somewhat similar setting (depot-level maintance on inertial guidance systems for military aircraft and guided missiles) from 1966-70, and the equipment I see in the film looks significantly more primitive than what I used.

 

[triod750]

the equipment I see in the film looks significantly more primitive than what I used.

I can't stop giggling when thinking of this. Well, in between I laugh out loud! Impressive indeed!! .

 

[whirlwind]

Listening to an Eric Gales playlist this morning with the VC and these five pretty maids...all in a row.

@Monsterzero Has you amp made it's way back to you?

 

[Monsterzero]

Listening to an Eric Gales playlist this morning with the VC and these five pretty maids...all in a row.


@Monsterzero Has you amp made it's way back to you?

It has indeed. Unfortunately my VC has made its way back to ZMF. Somewhere along the way,I lost bass response from the VC. Zach asked me to take the black grilles off and snap a couple photos of it, which I did. He couldnt ID anything obvious from the pics, so off it went.

In the interim Ive been listening to the VO, and although Keenan did a fantastic job on my amp, ive not been able to replicate the depth and height out of the VO as I was with the Airmid (RIP).