New, Homebrew 40/20 meter water cooled amplifier..

[VK3ZL]

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..

[VK3ZL]

This is my very simple workbench where I build all my projects....I mainly use simple hand tools for all my work...I built a metal bending brake 25 years ago and still use it....I have a 3 speed drill press and a small lathe for light work making shafts etc....I sometimes spend hours locked away in here figuring out and building stuff...

Bob..VK3ZL..

[KG4CGC]

Amazing stuff!
One day ... I hope to clear out a work area combined with the operating position and the computers.

[KG4CGC]

Not that I could ever do anything as amazing as your work. :yes:

[VK3ZL]

Not that I could ever do anything as amazing as your work. :yes:

Charles, You are an artist making drinks for the Island members and I partake with much relish, often..:yum:...I am sure that your talents would extend to even greater ambitions if you apply yourself...:yes:

Bob..VK3ZL..

[N9FE]

Very Nice. Very clean and organized. You and a friend of mine W9TKO should get together. You two have the skill i'm tellin ya.

[KG4CGC]

Charles, You are an artist making drinks for the Island members and I partake with much relish, often..:yum:...I am sure that your talents would extend to even greater ambitions if you apply yourself...:yes:

Bob..VK3ZL..
Thanks!
At my age I have collected a few tools. Problem with tools is that they have a distinct habit of sprouting legs. Even the ones bolted down to the floor.

[NQ6U]

Nice job, Bob--those cooling manifolds are a work of art, especially when the minimal amount of space and equipment you have to work with is taken into account. I like your use of the vacuum variable cap, too.

[VK3ZL]

Nice job, Bob--those cooling manifolds are a work of art, especially when the minimal amount of space and equipment you have two work with is taken into account. I like your use of the vacuum variable cap, too.

G'day Carl....Thanks for the comments.. I don't need a lot of bench space for these projects...Storage for components and all the stuff that goes into an amplifier takes up much room....I can put an amplifier together from scratch in about 100 hours including hand making the case which on an average takes me 25 hours....Vac variables are great although they are scarce in VK and cost lots to bring in from overseas...Postage is a real bummer also these days....The cooling manifolds are fairly straight forward to make and I use silver solder to put them together....This means fluxing all the joins and heating the whole cooler at once to make the silver solder run...Guess it's a one chance job and you can't make a mistake....The rest of the amplifier building is fairly easy once the chassis is finished and the main hardware is installed....I hate wiring up....I never have confidence in relay and switching and have to concentrate very hard to do it all properly....However the end product once finished is reward itself once I put it on air....My shack amplifiers are all water cooled these days and I would never go back to noisy dusty blowers....

Bob..VK3ZL..

[PA5COR]

Suying that i'm deeply impressed is the understatement of the year...

Back to antenna's , picked up a titanium/alu mast of 7 foot sevtions, total length 66 feet.

Too hot, 34 degrees outside, so it'll have to wait for building it up...

[K7SGJ]

That is truly a work of art, or should I say Bob. I am always amazed at what a craftsman is able to do in the absence of modern, computer controlled shop equipment. It is sad to think in a few decades old world hand-crafting will be a lost skill. Nice work!