View Single Post
Old 5th Dec 2019, 1:51 pm   #33
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
Default Re: "Burning - in" Double Triodes

So the question here seems to be;

“During the initial period of use, do valves change their characteristics such that either;

i) the change is measurable using a either a simple DC test set or a VCM
ii) The change has a demonstrable effect on the performance of the equipment the valve is being used in”.

And the follow-on question is whether data exists that proves anything one way or the other?

I’ve spent quite a lot of time measuring the DC characteristics of valves in pursuit of having a good reference or “standard” valve(s) for use to check readings from my VCM163. The first valves I used for this were ECL80’s, then EF91’s and then I finally settled on ECC81’s (the reasons for this progression are significant but off-topic). In each case, I’d laboriously characterise the valve by hand on a DC test setup, paying due regard to accuracy and reproducibility (during the course of which, I verified Tanuki’s assertion that every amplifier wants to be an oscillator). What I will say is that the data I gained convinces me that that burn in does occur.

As David Simpson (OP) will recall when he initiated a comparison of valve tester measurements on this forum, the readings I got from my 163 on a valve which he had standardised were extremely close, so my “doings” have some kind of validation wrt the outside world.

But by way of other data, the attached PDF shows a plot of change in emission, taken from a paper called “Electron Emission for the Oxide Cathode” by C.H.Meltzer and E.G.Widell. This is from either an American book or conference proceedings in the early 1950’s, but the full reference was not supplied to me. I didn’t fake it and I’m sure that numerous other papers can be found showing the same thing – this was just the first paper I found in my files.

As for whether or not burn-in affects the performance of equipment, I have only my own thoughts on that and no data whatsoever on that, so I stay silent on the matter!

I'm sure that others have more data?

B
Attached Files
File Type: pdf emission w.pdf (281.9 KB, 78 views)
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.
Bazz4CQJ is offline