[R-390] R390 Restoration

[John Finigan]

Chuck,

Admittantly I know almost nothing about the 390, but I
happened to be reading the Collins engineering report
tonight for grins and came across this table for the
1st RF tube:

Distortion at .7V input (30% mod.)
6AK5 16%
6AJ5  3%

In short, they found it possible to get remote-cutoff
characteristics from the 6AJ5 by running it at high B+
but rated screen (I think??).  I have one laying
around and knew they were 6AK5's for 28V plate &
screen, but never have heard an explanation before.  

John



> Found the 1st RF tube replaced with a 6AK5 v/s a
> 6AJ5 as are all the 
> oscillator tubes.  Also, there is a 6BH6 as the last
> IF amp.   I wonder if these 
> are helpful mods AKA: W3HM and the 75A-4 mods or did
> someone popped 
> some tubes and just stuck those in 'cause they fit?




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