>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
- 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: http://www.contesting.com/FAQ/amps
>>Administrative requests: amps-REQUEST@contesting.com
>FAQ on WWW: http://www.contesting.com/FAQ/amps
>Administrative requests: amps-REQUEST@contesting.com
- R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.
FAQ on WWW: http://www.contesting.com/FAQ/amps
Administrative requests: amps-REQUEST@contesting.com