Subj : Re: Your First SSB XMTR
To   : Tom Walker
From : Holger Granholm
Date : Sat Jun 21 2014 10:13 am

In a message dated 06-20-14, Tom Walker said to Ed Vance:

Hi Tom,

TW> Speaking of "Final" Tubes I rembember from the 50's when I was on a
TW> Submarine for the Radar the ET's they had a board with a spare set
TW> of Finals mounted with the filiments powered.
TW> Seems like the tubes needed a break in because of you put a cold set
TW> in and hit them with the high voltage B+ they would fail.

That is the way old (even unused) should be broken in irrespective if
directly or indirectly (cathode) heated. The reason is that the glass
feedthrough always allow some of the vacuum to escape with age.

When the tube is manufactured the getter is used to burn the remaining
air away but after that the getter is useless. That is the purpose of
the pre-heating of replacement tubes and it also concerns old unused
spare tubes.

CU AGN, Sam, OH0NC

aka Holger

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