has anyone else experience this.....

Al, thanks for your comments, as that makes me feel better about my 752. I have had it for quite a few years, and over that time the results have always seemed to be consistent.

Also, some of my tubes came from my dad's shop, as he was a radio/TV serviceman, with many others coming from different shops in my area. I also collect some antique radios, mostly Zenith, and some HH Scott tube gear.

Cheers,
Tony

Hi Tony,

Regarding calibration, all I can cite is my own experience. I've had the 800A for a bit more than 20 years, and used it lightly from time to time during that period.

I have a very large collection of vintage tubes that I use primarily in conjunction with my antique radio collecting hobby, having acquired them from a retired radio/TV service person, various auctions, etc. I can say with high confidence that many of them are NOS in the true sense of the term (i.e., unused). On almost all of the many occasions I have had to test some of those NOS tubes over those 20+ years, their Gm has measured in the general vicinity of what it should measure, according to the chart on the tester as well as older GE and RCA tube manuals I have. That gives me confidence in both the calibration of my tester and its stability over time.

Best regards,
-- Al

Al, you're welcome. Always glad to provide helpful information.

The Brent Jesse site also has a lot of other good info about vintage tubes, as well as some instructional videos identifying certain vintage tubes. The following websites have many pictures of vintage tubes that may also help with that vintage tube identification.

tubeworld

tubemongerlib

I acquired the Brimar 12AT7's many years ago that I previously mentioned, and for quite some time was unsure about them being authentic, as they were different from all other pictures of Brimars I found. After finding a picture on the Tube World site, I then felt they were a real vintage tube. This was also confirmed when I allowed a few local friends to try them, and they did not want to return, but asked to purchase them.

BTW, I also have tube testers, a B&K 600 for quick simple testing, and a Hickok 752 for more serious testing. Although the Hickok seems to work reasonably well, I am curious about your thoughts on calibration of this tester.

Tony

TLS, thanks for the good articles, and the good points you provided in your post. As you and Bill_K indicated, the term NOS is unfortunately used too loosely too often. With the problem being further compounded by the existence of fakes, as Elizabeth pointed out.

As a potential purchaser, everything else being equal I would feel much more comfortable purchasing from a seller describing a tube as "used but tests as new" than from someone who simply describes it as NOS.

Also, I must say that personally I wouldn't want to be without a good tube tester (I have a vintage Hickok 800A), in part to minimize the possibility of component damage such as the OP has unfortunately experienced.

Best regards,
-- Al

I normally get my tubes from andy of vintage tube, put had been calling around talking with some of the other pundits selling tubes and got burned so to speak...

I agree with Al, that NOS should mean the tube has not been used in anyway whatsoever, however this is usually not true in so many cases.

Here are a couple of good articles by Brent Jessee about NOS tubes,

NOS Tubes: New Old Stock or Nasty Old Stuff?

A BRIEF NOTE ABOUT NEW OLD STOCK TUBES

Brent Jesse is a very reliable seller, but IMHO, some of the NOS tubes may possibly be slightly used, however do exceed rigorous testing for NOS. I have read many times that even a good slightly used old tube can still be much better than some of the new production junk. The problem lies with everyone acquiring old tubes calling them NOS regardless of the condition..

I used to questioned NOS tubes that did not come in original box, however found out that this means nothing. A poor used tube can easily be place in an original box. The box of a NOS tube may have deteriorated over years. Also, I have some very rare NOS Brimar black plate 12AT7's from 1955 that came in a bulk pack of 100, so no individual box, however, I do have the original bulk box.

Elizabeth also brings up a good point about tubes being relabeled, so it is important to know the physical characteristics of the internal structure for a particular tube.

It is always best to purchase from a reliable seller that offers a guarantee.

Actually most dealers worth their salt stipulate whether they are selling new NOS tubes, used NOS tubes that test like new or whatever. Almost every seller provides test results and point out if the results are "marginal."

that's what I think as well, actually they blew out my preamp, repair guy said it blew a resistor, was pulling 6amps which it should not have.............

Fake Mullards? What's next, fake Badboys? Fake Tung Sol Round Plates?

There is something wrong with the tubes, (they might just be
worn out? How used is used?) or your cj PV-10 just doesn't
play well with them or you just don't like them. Maybe time
to move on.

Sorry, but what you describe, isn't what I have found to be
true with NOS Mullards. I have been using these tubes for
over 30 years and still have bunches of them left. By far
"my" favorite tube, but definitely not for
everyone. As always, YMMV...

regardless, them turning lean after a short time of use is what im worried about. I talked back to who I brought them from and he informed me they were used nos tubes, I put back in a pair of Phillips/miniwatt Holland I had in before and the sound was fine again...........

As usual Al is correct, although many sellers claim that they are selling NOS tubes which are actually used.

i recently purchase a pair of mullards nos tube for my pv10 Conrad Johnson ....

they were used.............

A point of information: "NOS" = "NEW Old Stock" = unused.

Regards,
-- Al

they were used.............

How much time do you have on the Mullards? They need at least 40-50 hours to burn in.

I use Mullards almost exclusively and have never found what you state to be the norm. Maybe new, right out of the box, but never after they've burned in.

Give them some time to break in...