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

Bernie Doran qedconsultants at embarqmail.com
Tue Aug 25 12:49:06 EDT 2009

The milky white appears when the tube has lost its vacuum and fil power is 
applied, I have seen this vapor of death more than a few times when testing 
old fellows. This is not to say that this is the only reason for the white 
deposits, but it is the only way I have seen it form. Bernie W8RPW
----- Original Message ----- 
From: "rbethman" <rbethman at comcast.net>
To: "AM Radio List" <amradio at mailman.qth.net>
Sent: Tuesday, August 25, 2009 12:06 PM
Subject: [AMRadio] 100TH and 250TH advice and or comment

> Question:
> I have noticed that the 100THs and 250THS that are in their original
> boxes, either not used at all, or maybe use for less than an hour to
> test them, seem to be doing fine.
> Their envelopes are crystal clear an can not see any sort of defect.
> Then the ones that are in one of the two BC-610s that has the hours on
> it, even though it last performed flawlessly, now appears to have gone
> gassy with some milky white inside the envelope.
> Is this perhaps due to over heating or maybe I should phrase this as the
> convection cooling of these radios since they do NOT have fans.
> Ideas?  Comments?
> It has always been metered and watched with a scope for observing
> waveforms, and the wattmeter is the newer Model Bird with peak reading
> built-in.  (However true they really are!)
> Bob - N0DGN
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