Re: [TCML] 833A VTTC schematics

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

On 11/10/11 1:52 AM, Michael Mayer wrote:
> Dear William,

> 2. tube plate heats up red hot immediately after applying power, and the glass envelope definitely needs a cooling fan

These tubes cool primarily by radiation, not conduction.  While you do 
want cooling air to keep the glass below melting point (particularly 
around the pins), that's not an effective way to cool them.  Some heat 
is carried out through the pins as well.

Don't forget there is a vacuum inside, so the thermal transport is by 
radiation initially.  Some is absorbed by the glass envelope, but 
hopefully a small amount.  You need something cool and black next to the 
envelope to absorb the radiant heat and carry it away.  the worst thing 
is a shiny metal chimney, which just reflects the heat back to the plate.


> 3. to combat the red hot plate problem, I am in the process of building Steve's Staccato circuit which will then be added to the 833A filament via triac.
that's definitely a decent approach.. increase peak power while keeping 
average power lower.  Thermal effects are tied to average power, spark 
length to peak.
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