[Amps] water purity/conductivity in water cooled tube amplifiers

Joe nss at mwt.net
Sat Apr 14 20:49:33 EDT 2018


How about instead of "Water" use Mineral Oil or Transformer oil?

Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 4/13/2018 8:40 PM, Steve Bookout wrote:
> Hello all,
>
> About 10 years ago, I built two 'boilers' for GS-35b tubes, totally 
> for the heck of it.  To date, I have not actually used either one, as 
> building a new amp was not high on my list of things to do.
>
> In my 'past life, I did R&D, high precision machine work, so this was 
> a bit of fun, to build something different for myself FOR A CHANGE.
>
> My general plan was to use 3/8 inch silicone tubing, to and from, the 
> tube boiler.  In order to give myself some 'dielectric length', I was 
> going to wrap several turns of the tubing around a round form in a 
> single layer.  This would be kind of like coaxial choke some wrap on a 
> piece of PVC.      I think I would rather have 3 or 4 feet of 'series 
> water', than have the HV only 10 inches of water from conductive 'stuff'.
>
> Plan on putting a micro ammeter from a metal water fitting  to chassis 
> in order to measure the conductivity from the water to chassis, at 
> some point in the water circuit.
>
> I know that really pure water is actually corrosive and will do it's 
> best to gain ions in order to get to some natural level of 
> minerals/contaminants.    I built the coolers out of several pieces of 
> brass and hard silver brazed it all together.  I know the electrical 
> current will cause an etching or eroding effect of the materials in 
> the cooler, but I used what I had.   At this point, I have no idea how 
> often I will changing  out the water. Could be after only 10 hours of 
> use, or it may be 100 hours and the cooler may rot out in no time.
>
> So, I need to know what the 'big boys' do in industry.  At what point, 
> in uS/cm, do I change out the water? The metering of the water 
> conductivity would be measure 3 or 4 feet from the tube boiler (@ 3600 
> volts)  How many inches (feet) of 3/8 inch dia distilled/low ion 
> water, in silicon tubing, do I need to have between 3600 volts and gnd 
> (thru a meter?)
>
> This will all be in a rack cabinet, where space is not going to be an 
> issue.  Already, mocked up the cooling, with the boiler sitting flat 
> in an electric skillet on high, with water flowing to an aluminum 
> transmission cooler, being pumped by a 110 gal/hr submersible aquarium 
> pump.   After 1/2 hour, the in > out temp difference was only 2 
> degrees, so that is looking good.
>
> I was thinking about the small contact area between the tube 'stem' 
> and the water cooler.  For those not familiar with the GS-35b tube, 
> the large copper cooler, is attached to the tube body (plate) with a 
> tapered 'stem' of a few degrees. ( I measured it with precision 
> equipment and fitted it as it should be fitted, but I just don't 
> remember the actual angle -- 2 degrees/5 minutes sounds familiar...)   
> I was wondering if a thin coat of 'Arctic Silver', or some other heat 
> transfer compound used for CPU's, would be a good thing.
>
> 3600 volts on the plate.
>
> Would love to hear comments about any of this.  None of this is fixed 
> in 'stone'.  Just my general plans.
>
> 73 de Steve, NR4M
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