[Amps] Ceramic tube temp too low?

[John Lyles]

Didn't see your call sign but assuming you are building this for 
licensed amateur service, here is one opinion. You cannot damage a 
ceramic metal tube with too cold liquid, within reason. Two things may 
limit you, one being freezing point and other being the dew point. If 
you are in a humid climate, and happen to turn off the RF power, but 
leave the cooling on, you may find significant condensation on the 
surfaces within the amplifier, if it is below this point. We have done 
this by accident at the particle factory, where we had chilled water 
cooling a particular part (input circuit) of a big triode. With the 
filament off, and no RF, there was no heat, so it 'sweated' inside the 
cavity and was fireworks when the RF came back on.

John
K5PRO

On 3/14/16 10:00 AM, amps-request at contesting.com wrote:
> Message: 5
> Date: Mon, 14 Mar 2016 21:46:45 +1300
> From: Steve Wright<stevewrightnz at gmail.com>
> To:amps at contesting.com
> Subject: [Amps] Ceramic tube temp too low?

>
> I am thinking of liquid cooling VHF/UHF GS-35b tubes to dodge noisy fans
> and and tuning drift.
>
> But what will be the situation with operating these tubes at lower
> temperatures?  I cannot see that they have a rated operating range, just
> a maximum seal temperature.
>
>
>
> Steve