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[AMPS] RE: 3-500z cooling

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Subject: [AMPS] RE: 3-500z cooling
From: (2)
Date: Sat, 29 Sep 2001 10:44:35 -0700
>At 05:44 AM 9/29/2001 -0400, Tom Rauch wrote:
>> > No, it was the technically correct way to do it.  The tubes could be
>> > put into continuous service in some application (drivers for an AM
>> > broadcast transmitter for example) at 100% duty cycle, hence proper
>> > cooling was absolutely required to provide reasonable life.  Hence
>> > Eimac's recommendations.
>>respectfully Phil, the correct way to do it is any way that maintains
>>the envelope and seals below rated temperature.
>>How you do it does not matter.
>Understood Tom.  I really didn't express my point very well with my first 
>post.  There's no question that as long as air flow maintains proper 
>envelope and seal temperatures, it doesn't matter how the air is 
>propelled.  What I meant to express was that as a manufacturer Eimac is 
>expected to provide recommendations for a proper method of cooling that is 
>tried, tested and proven.  Their centrifugal blower/chimney set-up was 
>their method that met those requirements.  And it appears to be a pretty 
>good method (although more expensive than the fan with horizontal air flow 
>method).  That provided an off-the-shelf solution so that manufacturers 
>wouldn't have to engineer their own cooling system.  Of Course that method 
>doesn't exclude the possibility of other and different cooling methods 
>producing the same result. And of course (and as you pointed out) there are 
>plenty of examples of simple fan cooling that have proven perfectly 
//  The Heath SB-220's transverse fan cooling system achieves lower glass 
temperature than an air system socket/centrifugal blower/chimney -- 
1.  a high-speed centrifugal blower is used that can suck the chrome 
plating off of a trailer hitch.  
2.  the Heath fan motor is not oiled peroidically, and the oilite 
bearings seize.
- The TL-922 also has transverse fan cooling, and it works, thanks to a 
clever baffling system

>There !  That's what I was thinking the first time but didn't say until the 
>second time.  The difference between a Friday night and a Saturday morning.
>> > The fan aimed across the envelope and filament pins work fine in
>> > amateur service where the duty cycle is generally low, low, low.  If
>> > you ran RTTY for an hour or so at full output with the fan method, you
>> > might find the limitations of that cooling method quickly.
>>Not so. Air flow is air flow.
>>It takes a much larger volume of airflow to cool a 3-500Z with no air
>>confinement, but you can do so at much lower static pressure and
>>the air coming out is not nearly as hot even though it carries the
>>same amount of heat. That is because it is more air volume.
>>Any system can be done improperly. The right way to cool a tube
>>is the way that keeps the temperatures below the ratings.
>>Many broadcast transmitters do not use chimneys, and many do.
>>73, Tom W8JI
>>FAQ on WWW:     
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-  R. L. Measures, 805.386.3734, AG6K,  

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