[Amps] Tube cooling

[Roger]

On 11/25/2010 7:47 PM, Robert Briggs wrote:
> I have completed my experiment cooling 2 x GI-7BT tubes in a new 6 meter
> amplifier this morning...
Put the tubes in a compartment all by themselves.  Then they are 
essentially in a duct with the lower portion being pressurized and the 
top compartment being at a reduced pressure increasing the air flow even 
more. The approach is notably more efficient than just adding a fan to 
exhaust warm air.

73

roger (K8RI)
> An additional thought
>
> Final result is two 3.5 inch 240 volt muffin fans on the bottom cover
> blowing directly on to the filament cathodes then exiting through the
> sockets and chimneys...I added a 5 inch 240 volt muffin fan on the top
> cover drawing the air up away from the tube anodes....Result is a good
> air flow sufficient to keep the tubes fairly cool under operation....The
> fans are reasonably quiet so I see no problems cooling the tubes this way...
>
> The main thing is to have the bottom fans offset so that a direct air
> flow is blowing on to the cathode filaments and making certain that
> there is as little restriction of the flow through the sockets as
> possible...The addition of another muffin fan on top makes sure that the
> hot air is drawn out of the cabinet...I am quite pleased with the result....
>
> Bob..VK3ZL..
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