[R-390] Tube Tester

[Veenstra, Lester]

While tube testers are fine for gross checks, an evaluation of real
goodness, that is, gain at RF, or at IF or at AF, or IF AGC Action, or,
and particularly, front end noise, is best done by substitution in the
receiver, finding better, best, or in many cases, does not make any
difference, tubes.

The exercise of testing nominally good tubes in a tube tester and using
that data as a predictor of which is the best in a critical spot in the
receiver, is not one I would waste time with. Of course all the above is
predicated having a receiver available that is in reasonable good
condition. From that point, running substitution checks with the
available stock, is a way to get reasonable condition up to really hot
condition. 

Still, would like to see design of the $1.95 do it yourself tube tester!

      IMHO
           Les  K1YCM/3

-----Original Message-----
From: John Lawson [mailto:jpl15 at panix.com] 
Sent: Tuesday, October 26, 2004 12:51 PM
To: Veenstra, Lester
Cc: R-390 HF Receiver List
Subject: RE: [R-390] Tube Tester




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