ORIGINAL MESSAGE:
On Mon, 7 Sep 2009 10:26:42 -0400, "David J Windisch" <davidjw@cinci.rr.com>
wrote:
>Does a 3CX800A7 require airflow any time the filament is lit, like, say,
>3-500Z glass tubes with tender seals and 70-watt filaments?
>
>I'm thinking of leaving the (unobtanium) blower turned off, to lower wear and
>tear, until I need the power.
>
>Yep, I'm aware of the potential hazard of a senior moment: I have in mind a
>no-blower-no-operate interlock scheme.
REPLY:
Personally, I would not risk it with such an expensive tube. The answer to your
question, and the only way to be sure is to measure the temperature of the
metal-to-creamic seals and make sure they do not exceed 250 degrees C.
As the data sheet says: "It should also be noted that it is not good practice
to operate at, or close to, the absolute maximum temperature rating for the
metal/ceramic seals. Where long life and consistent performance are factors
cooling in excess of normal requirements is normally beneficial."
Words for the wise.
73, Bill W6WRT
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