How to test those NOS tubes

Detlof:...I have near your knowledge / maybe less. My amps are the individual socket biasing type. As in CJ Premere5s.--16 el34s--16 trim pots.

I bought a set of 16 of these nos's--The seller told me these were tested 14 way to sundown. However, 4 wouldn't bias at all.-- In these amps you follow the instructions in the book; baisiclly,insert the tubes,turn all the trim pots back to zero,turn on the amps, turn on the pre no volume. after a few minutes bring the trim pots up till the led glows/ then trim pot goes back, to just extinguish the led. On the 4 that wouldn't bias ; means the led wouldn't go out - at all. I tried the 4 in different sockets/ and the other mono--same result.(Blew 2 fuses in the process)

Ok, A novel to ans your query??--Sorry. My point is that no matter how *these* tubes were tested before I bought them;It didn't matter.--They just wouldn't bias in my amps.No I don't know what gremlins were at work here. A tube tester may not tell you all you want to know-(as in my case)

Wow, what a story, George. Luckily I don't have to bias my power tubes. What I need to measure and match especially are those preamp double triodes and to find those with the least noise.

Detlof; As you might surmise from my previous confession, I'm no help at all. I'm still learning. But every thing I posted regarding output tubes is an actual experience. My education has a ways to go--in all areas. I'm not sure if this "tests well- won't bias" carries over to the pre amp or driver tubes. Where are the guys with the *big brains*?

Detlof: I am pretty sure that special test amps are needed in order to measure noise. Maybe there is a way (with additional equipment) to test them while running in your amp, but this is just a guess? Most testers just measure for GM and MU (think that's it, haven't used one for over 25 years) and may have a feature that will allow you to drop the current down approx. 10% while they are still in test mode in order to see how much the first reading drops. Generally the greater the drop, the less life left in the tube, but there may be exceptions to this. I am far from an expert and just followed the test instrument's instruction manual when I used to test tubes for my guitar amps. I purchased my Hi-fi tubes new (as needed) at this time and never bothered with it, but then again I had never heard of NOS tubes 25 years ago. LOL. Speaking of 300B's (I am a fan of the late production Svetlana's from Conus Audio in Canada) there is talk of a new TJ Meshplate at AA that looks very interesting.