On 11/26/2011 02:52 PM, Antonio I0JX wrote:


"Scott Dorsey" ha scritto nel messaggio
...

Right. The emission tester isn't testing the gain of the device or the
transconductance... all it is testing is how effective the cathode is
at emitting electrons.

How effective that is has to do with the surface area of the cathode, with
the temperature of the cathode, and with the composition of the cathode.
But you can be reasonably sure that most tubes of a same general technology
will have the same general emission. So if you pull some generic octal
tube or some generic miniature 9-pin tube, you can make a pretty good guess
what the emission is going to be.

-------
I am aware that the Lafayette tube tester only indicates one parameter,
i.e. emission. As a matter of fact tubes showing almost the same
emission on the Lafayette, instead show a very different performance on
a professional tube tester (AVO).

But is still unclear to me how can a tube drawing a 0.3A filament
current (e.g. a 6AU6) show the same emission of a tube having 2.5A
current (on the Lafayette) .

73

Tony I0JX
An emission tester will give a good account of the condition of many
power tubes especially rectifiers. On small signal tubes a
transconductance tester is required to get a good idea of the tubes
performance.