GS-31B 160 meters .. Water Cooled Amplifier...Bob..VK3ZL..

[VK3ZL]

Hi all,  I was looking to start a new home brew project a few months ago and decided to build a water Cooled 160 meter amplifier using a Russian GS-31b triode...The GS-31B and GS-35B tubes are excellent for this project as they have removable coolers...After a bit of research I got together some copper tubing and sheet and my good friend VK3HAH Reggie built water manifolds for both type of tubes...I spent quite some time planning out the project and started gathering the components for the amplifier...The vacuum variable capacitors and HV doorknob capacitors were sourced in Ukraine along with the tubes..I had the HT power transformer custom built to my specs by Jeff W8CQ from Harbach Engineering in the USA...He produced a beautiful Hypersil transformer for me, 48 pounds weight, but a compact 8 inch cube..I hand made the cabinet and front panel along with various RF chokes and all the small parts needed to assemble the unit..

The job is close to completion now...All functions have been tested and perform to specs....The amplifier has a grid current sensing circuit with a reset function..If grid current reaches a specified level the circuit trips a relay returning the amplifier to cutoff..There is a reset function to put the amplifier back into idle mode..

There is also a variable cathode bias circuit..I can select amplifier standing current from the front panel, 0ma CW to 150ma SSB..

I started building this amplifier 6 weeks ago and nearing completion at last..I only have to install the Hypersil transformer and connect the water cooling module also install the new meter scales..I will add further pictures and comments once I have completed the project and have it running in the shack..
Bob..VK3ZL..

[VK3ZL]

More pictures.

[VK3ZL]

Even more pictures.

[VK3ZL]

Still more pictures.

[Anthony Pappin]

Hi Bob. Thats an amazingly well built unit for home brew. I used to be a refrigeration mechanic until I had a bad work accident. Water cooling is very interesting to me. Are you just going to use plain water or some sort of coolant that you use in a car? I believe the coolant, green stuff, has better heat transfer properties than just water. What sort of work do you do, or did, as you have some very good skills at working with metal and electronics? Very Interested to hear how this project performs. 73s, Anthony in Colac VK3.

[VK2NET]

Hi again Bob, I''ve created two images which will explain how to add images to a post, hopefully they will get you uploading successfully 

Please look at the two images below plus some text I added.

[VK2NET]

Hi Bob, I just knew you would capture Anthony’s attention the instant you mentioned ‘Water Cooled’ and that image of the car radiator, that would have sent him over the top, I think you have found a true friend here because Anthony is just besotted with making things and his speciality is using common household objects that are not expensive and readily found around the average home. 

[VK3ZL]

Hi Anthony and Ron...I finally sorted out how to load images with the help of my XYL...She has a bit more pc savvy than I do...

To answer your questions Anthony..Firstly I am very electronic illiterate and have just learned as I go...I have always loved creating thing with my hands using only basic tools...I always try to pay attention to detail when I am building things..If I am not happy I will start again until I am satisfied..

Regarding water cooling...There is little basic hands on information on the internet and as this is my first go at it I finally got on to some radio engineers who work in the broadcast industry....In short I will be using distilled water in the cooling system and nylon hose to and from the reservoir...The safe length of hose is 1000 volts per meter so I will be using 3 meters in both the input and output hoses...I will be using a 1000 liter per hour submersible fountain pump to circulate the water...I expect a flow rate of 4 liters per minute through this system..I will have a ma meter from the reservoir to ground to monitor leakage current...The water becomes contaminated due to leaching from the copper manifold and also the radiator which is cooled with a 240 volt muffin fan.I will have to change it on a regular basis..I am trying to find a much smaller radiator than the one pictured as it is bulky and really too large for this job..I will have a 20 liter reservoir and I doubt the anode dissipation will heat that too much...It would have to be a long over Hi....I hope this answers some of your queries...

Bob..VK3ZL..

[VK2NET]

That''s a great description Bob, it seems you have planned it very well. As far as a smaller radiator goes, I’m sure you are already on the lookout at the local car wreckers (not sure if you have any in Tassie) for a Mini or similar small car, any of the older vehicles like Austin’s etc, will have small radiators but these may be hard to source in your QTH. 

[VK3ZL]

Well I have at last finished the GS-31B water cooled 160 meter amplifier...Over the past few days I connected the water pump, 3 meter vinyl water transport hoses and water reservoir....I am using 10 liters of "Pure" water in the reservoir..The water pump is a 12 volt 1000 liter per hour pond pump..Measured water delivery through the cooling manifold on the tube is 4.5 liters per minute...At the reservoir both inlet and outlet hoses have a copper joiner bonded together and I have run a grounding wire through a 1ma meter to read leakage current to ground...This is also a safety measure as there is 3000vdc in the water lines...Leakage current is 320ua cold and in operation the leakage current is 500ua @ 40*C..

After testing all electronic functions of the amplifier I was satisfied that everything was working as I designed it to...Today I connected the amplifier up to an Icom 737 for RF tests...The amplifier tuned up correctly first try and using 10 watts I was able to establish resonance on 1.830mhz, load and dip...10 watts drive produced 205 watts output...I then brought drive up to 60 watts carrier and Anode current was 800ma @ 2800vdc with loaded grid current 220ma..Output into the dummy load is 1300 watts + - 20 watts...I then ran the amplifier for 1 hour both carrier "key down" and cw dots 60wpm speed....After 30 minutes the water warmed to 40C in the reservoir and leakage current is 500ua....This is well within my design criteria....The amplifier will produce over 1600 watts carrier output with 80 watts drive but that is getting close to tube saturation...In other words, more drive won''t produce more power..I am satisfied that the job is complete and ready to be moved into my shack...

After finishing this job I am convinced that water cooling amplifiers is the way to go..Much better efficiency and no blower noise to contend with..In fact this amplifier and water system is virtually silent..

I will add a few more notes after I put this unit to use...I am already laying out two new 2 meter amplifiers using water cooling...I will be using GI-7BT Russian triodes in these projects....These tubes have proven reliability and at $25 each they are excellent value....

73 all...Bob..VK3ZL..

[VK2NET]

Absolutely sensational Bob, well done indeed, I hope you can post a few images, so we can see it, kudos to you