Exactly right. Test results mean nothing in determining NOS.

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In Reply to: That doesn't always help either posted by DrM on July 30, 2002 at 08:02:45:

You are exactly right.
A tube tester will tell you how the tube tests against a nominal standard. That has virtually nothing to do with whether it is NOS.
So your new 12AU7 tests at 100%. Whoopee! Is it NOS? Well, if it is a Telefunken, probably not. A real NOS Tele usually tests at about 120% - but if it tests at 120%, it's not necessarily NOS either! That's because, as you say, tube emission does not drop of in a linear fashion over time. They stay testing pretty much as new for a long time - then start dropping off steeply. That's the quandry of buying used tubes, particularly on Ebay - some people take the tubes out of their eequipment after a couple of years, when they still test great, stick 'em back in the boxes, and sell them - before that downhill curve sets in.
But let's get back to that new tube that tests at 100%. I said, if it's a Tele, it has a good likelihood of being quite well used. What if it's a Tungsol 12AU7? In that case, it may very well be new or close to it - new Tungsol 12AU7's, particularly early ones, test in the 90 to 100% range.
So what can be concluded from this? Absolutely nothing, and that's the point. A tube tester t4ells you transconductance, shorts, gas, and so on. No matter what the measurements are they in no way can prove thhat a tube is NOS. Nor can the box, as I described above, nor can how the tube looks. I have many tubes that are NOS with very much less than perfect printing. They rub inside the box, they have been taken out of the box and smudged by a thumb, and the printing was never meant to be permanent anyways. They're old, for crying out loud.
As you say, there is one certain way to determine if the tube you are getting is nOS. Buy from a good dealer.

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Follow Ups Full Thread

Topic - tubes: what does NOS stand for? - hukkfinn 15:08:28 07/29/02 (8)

Re: tubes: what does NOS stand for? - Mick Jones 17:23:10 07/31/02 (0)

New Orleans Saints - Todd Krieger 15:35:37 07/29/02 (5)

I don't know why... - Daryl R 22:05:30 07/30/02 (0)

Re: New Orleans Saints - Jim McShane 06:59:50 07/30/02 (3)

Get a tube tester - Ryder 07:54:24 07/30/02 (2)

That doesn't always help either - DrM 08:02:45 07/30/02 (1)

Exactly right. Test results mean nothing in determining NOS. - Robert H. 12:20:42 07/30/02 (0)

Re: tubes: what does NOS stand for? - LesBMoore 15:25:27 07/29/02 (0)

Follow Ups

Exactly right. Test results mean nothing in determining NOS. - Robert H. 12:20:42 07/30/02 (0)

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