[AMRadio] 100TH and 250TH advice and or comment

rbethman rbethman at comcast.net
Tue Aug 25 18:53:57 EDT 2009


I'm thinking the thermal cycling, a number of years of use that is for 
the most part intermittent, followed by then sitting for another year 
and a half has been what broke the back.  So long as the intermittent 
use was a rather regular periodic interval, I was heating them up and 
getting them full use.

I got medical issues that wouldn't let me enjoy the big AM rig, and it sat.

I started trouble shooting a problem, and I find the three of them are 
now gassy.

Yet the second radio only got used for about two hours since I got it, 
(I can only run one at a time. LOL), and it has now sat for over four 
years AND it has NO gassy tubes.

I trying to understand why ONE did and the OTHER did not.

Then it could just be those tubes were going anyway.  Although I doubt 
it.  They all can in the original Mil issue packaging.

It is all strange!

Bob - N0DGN

Brett Gazdzinski wrote:
> I have a modulator that uses four 100TH tubes, it has had the same tubes for 
> the last 25 years, they look clear, and work fine.
> I have a bunch of spare 100 TH and TL's, all look ok last I looked...
> I have noticed a bunch of white tubes in the 7 and 9 pin tube stashes, maybe 
> the seals fail, the pins rust, or something happens and the air gets in.
> You have a lot of thermal cycling on tubes that get used, from cold to very 
> hot, to cold again, but tubes just sitting going bad?
> Brett

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