I ran a 4CX1000A at 100 MHz, 1.5 kW CW, with a plugged cooling duct years ago.
It started drifting out of tune, and eventually baked some of the nickle
plating to a dark tarnish. It was still working, but
quite far out of tune, i suspect that things were warped inside.
Another approach is to use a cord or spring, with a temperature sensitive
polymer thing attached to the tube. This melts at some temperature and the
spring retracts and lets go an interlock contact.
John
K5PRO
> 1. The cut-out mechanism would be one of these TO220 sized bimetal switches.
> They are available in a variety of trip points.
>
> 2. The switch has no electronics inside and should be RF immune.
>
> 3. The switch can be set in the chimney near the silicon wall and would not
> significantly impede airflow.
>
> 4. The switch has a very low thermal mass and will switch quickly.
>
> 5. Even with a failed blower, the tube would be dissipating tons of heat and
> convection would ensure heat-up of the switch.
>
> 73, Jeff AC?C
> www.ac0c.com
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