[Amps] Miller-Larson effect on thoriated tungsten filaments

[Mark Bitterlich]

Actually Carl, not to disagree but I saw a lot of 3-500's with "bad 
filiments".  But in truth, they were not bad.  Instead a cold solder joint 
had formed in the tube pins themselves.  Resoldering them normally fixed the 
problem, and so did keeping a close eye on the sockets.

When I was in the Marine Corps (which is to the Navy as is the chain on an 
old toilet... part of it, but not IN it), we used to modify the Collins S 
Lines so as to keep the filiments on ALL the tubes turned on constantly. 
The primary goal was to reduce drift, but the Reps from Collins also claimed 
it would extend the life of the tubes.  Hard to make specific claims as to 
whether it worked or not.

Much ado about nothing to some.... interesting information to others.


----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Mike Waters" <mikewate at gmail.com>; <amps at contesting.com>
Sent: Tuesday, June 25, 2013 9:14 AM
Subject: Re: [Amps] Miller-Larson effect on thoriated tungsten filaments


>I doubt if that has much effect on our low power tubes Mike but the "boys" 
>with the 10-20KW rigs might be interested.
>
> I also never had to replace any of the WW2 era TX tubes while in the USN 
> and those were cycled on only when necessary.
>
> Much ado about nothing for this forum. When was the last time you saw a 
> 3-500 with a bad filament?
>
>
> ----- Original Message ----- 
> From: "Mike Waters" <mikewate at gmail.com>
> To: <amps at contesting.com>
> Sent: Tuesday, June 25, 2013 12:32 AM
> Subject: [Amps] Miller-Larson effect on thoriated tungsten filaments
>
>
>>I discovered some new (to me) information on maximizing the life of
>> amplifier tubes with thoriated-tungsten filaments. I just uploaded it to:
>> http://www.w0btu.com/miller-larson_effect.html
>>
>> Basically, every time the tube filament passes through a certain
>> temperature range as we turn it on (or power it down?), we shorten the 
>> life
>> of the filament, due to the Miller-Larson effect.
>>
>> I would appreciate any comments on it, good or bad.
>>
>> 73, Mike
>> www.w0btu.com
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