[AMRadio] Ever seen this?

W5OMR/Geoff w5omr at satx.rr.com
Wed Oct 5 12:13:52 EDT 2005

Todd, KA1KAQ wrote:

>Geoff -
>I've read a little bit about transmitting tubes that sit for long
>periods releasing molecules that can form gas inside of the tube.
>Someone came up with a procedure for de-gassing them with a home built
>jig of some sort, to run them for a period of time getting them hot
>enough for the getter to absorb the gasses and other crap that had
>been released while dormant. It involves little or no voltage beyond
>the heater itself.
>Can't comment on your particular situation or the mechanism at work
>with the low voltages, but it sure sounds like one of those tubes that
>was otherwise good, but went gassy from sitting idle. Hopefully
>someone with more knowledge on the subject will comment. I have a
>number of old transmitting tubes in storage and worry about this very

I put that tube in the opposite socket after applying B+ (the blue glow 
went away) and disconnected the plate lead on the opposite side... that 
tube now draws 0 plate current.  I probably killed it.  In this process, 
I started testing some of my spares... another draws little or no 
current, one only comes up to about 150mA of plate current, when tuned 
off resonance, another up to around 150mA -at- resonance, (1500vDC on 
the plates) but tuning it slightly off resonance causes that particular 
tube to go into a run-away current situation. 


only 6 more to test, but they'll have to wait.  Gotta pack for a 2 day 
trip, leaving this afternoon.


More information about the AMRadio mailing list

This page last updated 23 Feb 2018.