G'day all....These are pics of my new 40/20 meter water cooled amplifier....I am using Russian GI-6B triodes in this project....Picture shows two types of the little triodes with my home brew coolers...The cooling manifolds are tricky to make...I machine up a solid copper center slug with a thread to screw down on to the tube anode...After all parts are made I silver solder them together with the two brass inlet and outlet tubes...I have to heat up the entire cooler to get the silver solder to flow evenly across all the joins....When they are cold I machine the base to make good contact with the tube anode..
Picture's show the front of the finished amplifier, then the RF deck with the two tubes with water coolers and the inlet and outlet vinyl water hose harness...These then run via two 10 foot long vinyl hoses to the water cooler reservoir, pump etc...
This amplifier is two band 40 and 20 meters optimised for best efficiency on both bands....The HT supply delivers 2900 volts dropping to 2500 volts under an 800ma load....Water flow through the manifolds is 2 liters per minute from the 12 liter reservoir...This is ample to keep the tubes very cool even under long CW sessions, contesting etc..
To select the two bands I employed a vacuum relay on the Pi output network and a simple cradle relay on the cathode input pi networks..This compact little amplifier really sings and has been a pleasure to build and use..
My next project is a 2 meter water cooled amplifier using the same tubes....I will post more details when I finish it....
Enjoy...Bob..VK3ZL..