[Hallicrafters] Tube life question

[Energyconserved at cs.com]

Greetings to all:

       A year or so ago I purchased a S-38E at a swapmeet.  This is a basic 
5-tube special with shortwave.  I noted at the time that the RF tubes were 
still the original Hallicrafters (dated early 1958) but that the rectifier 
(35W4) and audio amp (50C5) had been replaced.

       Radio sensitivity and audio were weak.  Not having access to a tube 
tester, I replaced all 5 tubes.  Problem resolved.

       But it got me thinking:  What's the expected life of vacuum tubes?  
Googling on "Vacuum Tube Life Ratings" delivered some discussion on tube life 
and extension for high power transmitting tubes but didn't talk about the 
receiving tubes.

       I'd guess that tube life is driven by cathode wearout (unless for 
instance the filament opens).  Probably a function of cathode current (or the 
ratio of cathode current to the tube rating).

       Can any of you Hallicrafter experts give a thumbnail on life 
expectations for receiving tubes?  

       Thanks!

       Regards
       WB0AJS
       Proud hallicrafters owner since 1999
       Hallicrafters      S-38E
       Kenwood          R-600
       Kenwood          R-2000
       Sangean           ATS 606 A
       (past rigs)
       National            NC-121 (my favorite)
       Eico                 723
       Galaxy             V MK III


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