[Amps] Tube cooling

[Robert Briggs]

I have completed my experiment cooling 2 x GI-7BT tubes in a new 6 meter 
amplifier this morning...

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..