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I have seen various posts saying that military designation ended with tubes made after 1945. I think VT-231 was used after 1945, but don't have any specific knowledge of the cut off date. So my question, does any one know when it was officially dropped?
Steve
Follow Ups:
The 2 types maybe the same physically but the military contract may also specify various parameters they wanted like higher reliability or matched sections, low microphonics, etc. This would mean that the milspec tube would be tested more thoroughly than civilian tubes. Extra testing would eliminate almost any dud before it reached the field. As an examply IME, i found that a NOS Sylvania VT231 displays low noise levels whereas the same style NOS Sylvania 6SN7GT is more microphonic among a batch of tubes. cheers, Dak
"...the milspec tube would be tested more thoroughly than civilian tubes"
It would be nice if that were true, but I think in fact the opposite probably occurred. The pressure to meet contract deadlines was severe during the war. I've heard stories from more than one person who worked on the lines about aircraft radios like the ARC-5, SCR-522 etc. being shipped out the door and installed in planes without even being tested. They were probably tested in a rudimentary way after installation, but nothing like we would expect from a factory-certified unit. I would be very surprised if the same thing didn't happen at tube factories. The poor quality of large numbers of 807s made in those years may attest to that.
--------------------------
Buy Chinese. Bury freedom.
VT-231 implies pre 1946 but they are no different than civilian tubes of the same era. 'We' just think they are better. ;-)
Same goes for UK government labelled tubes . Often more coveted due to the 'CV' designation and hearsay that these are 'mil-spec' and therefore better . Well I cleared out a UK nuclear power station of it's tube stock and these all had government markings , mainly as the power station would have been run by a government institution prior to privatization and would have sourced via the government ministry of supply . Same goes for the Post Office and the railways , these also used government marked tubes . Just because a JAN marked tube was made for the military , it does not mean it was 'mil-spec' . Same spec yes , but not 'mil-spec'
Al
I an aware of the popular but untrue thinking that VT-231 implies something special about these tubes. You are correct as far as I know that it doesn't mean anything special beyond it being a military designation.
Steve
I would tend to think the opposite. I read a lot of electronics industry mags from the 1940s and 50s.
A tube manufacturers in the war years would set a different (tighter) tolerances for different QC checks during the manufacturing process, as well as on completed tubes. Same construction, same tube in most cases, but a greater assurance that it meets or exceeds specs and performance, and that's what the military needed....assurance that those tubes put in use in rockets, jets, ships, radios in the jungle, etc., operated, they best they could with minimal failures.
"I can't compete with the dead". (Buck W. 2010)
"A tube manufacturers in the war years would set a different (tighter) tolerances for different QC checks during the manufacturing process, as well as on completed tubes."
Not just the war years but all tubes supplied to the military in any year.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It was more about filling contracted orders. AT&T had VT229 tube contracts filled by Sylvania and the boxes state as much but some believe the tubes were produced by AT&T. So it goes.
There were many exceptions like the 596 rectifier, Bendix Red Bank tubes etc. but most were just cranked out in volume. Normal good quality stuff.
It was really about the $$$ in the contract, not the quality of the product. The Pure Food and Drug Act was signed by TR because of nasty food
provided to the army during the Spanish American War. Nothing has changed.
A little follow up-
Given the age of most of these tubes it has been very hard as a hobbyist to experience any significant difference in quality between the VT-231s and commercial tubes.
If the really military did insist on tighter specs why stop at WWII? Wouldn't that have continued through to the early Vietnam era? Thus my question- VT-231 stopped when?
Steve
What differences are you looking for? Sound? The sound a VT-231 makes in a piece of audio was not a concern in its manufacturing. I sold three recently, and could not tell the difference between any of the VT-231s and a Japanese something that's in the preamp now, or whatever happened to be in the slot that day.
"I can't compete with the dead". (Buck W. 2010)
Why stop?They're called transistors and circuit boards, miniaturization, lighter loads, reliability, production speed, cost savings.
"I can't compete with the dead". (Buck W. 2010)
Edits: 09/18/15
Western Electric didn't stop production of the 300b until the military stopped buying them in 1988.
Just saying....
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Yes I recognized the advent of the transistor by saying it would have lasted until the early Vietnam war era. It did not even get though the Korea "conflict" wouldn't that have required tighter spec tubes as well. It is unlikely that they changed the machines to make the VT-231 tubes, I would think they might have been selected by various quality control stations along the way of manufacture. Just guessing...
In any event you and I agree that any improvement in building the tubes didn't translate into any obvious change in sound quality.
Steve
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