[R-390] Tube Tester

[John Lawson]

On Tue, 26 Oct 2004, Veenstra, Lester wrote:

> However, to play devils advocate (and CTM)  The best tube tester is the
> R-390 with a signal generator.
>   Les K1YCM/3    www.r-390.com
>


   With the possible caveat that one needs to be very sure of the 
'goodness' state of all the other devices in the radio, else a complete, 
calibrated signal-trace is required to insure that all other stages, with 
the exception of the 'stage of interest', are of a known-on-spec 
condition.

   Otherwise, you get into the -two and -three and -nnn unknown variable 
chaos.

   That being said, using a "perfect" R390 for substitution testing of 
suspect tubes is fine, again with the caveat that you can meaningfully 
*and* accurately measure the change in the system caused by the 
substitution, and then relate that back to the Tube Under Test parameters.

   This gets easier if the radio simply fails (or smokes...;{  ) when the 
substitution is made.

  On the whole, my own preference is to use a tube tester of some kind.


   Just my 200 millidollar on the Subject...


  Cheers

John  KB6SCO