[ARC5] Quick sensistivity comparison

[Richard Knoppow]

----- Original Message ----- 
From: "J. Forster" <jfor at quikus.com>
To: <kgordon2006 at frontier.com>
Cc: "ARC5" <arc5 at mailman.qth.net>
Sent: Thursday, June 13, 2013 10:33 AM
Subject: Re: [ARC5] Quick sensistivity comparison


> In my experience, just about all WWII vintage receivng 
> tubes can benefit
> from some gettering time.
>
> I just put them in a tube tester, adjust the grid for the 
> suggested plate
> current, and lo9ck down the TEST button and go do 
> something else for a day
> or so.
>
> -John

    I have just been reading a large tome on tube design 
published long ago by RCA. The types of getters used in 
receiving tubes changed at varous times. The earliest 
getters relied on ionization for maintaining the vacuum, 
later getters less so.  However, where tubes have been cold 
for many years its possible the conditions for "keeping" the 
vacuum have not been met. Operating the tube with some 
voltage on it may activate the ionization part of the 
getter.  Of course there is also the question of how much 
gas came out of the parts or got in through the seals.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com