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

To: "Roger (K8RI)" <>
Subject: Re: [Amps] water purity/conductivity in water cooled tube amplifiers
From: Kim Elmore <>
Date: Wed, 18 Apr 2018 22:18:57 -0500
List-post: <>
While it was a very long time ago, I recall as a kid I got to go on a tour of 
the old KVOO AM broadcast station in Tulsa. Their tubes were water cooled and I 
recall the engineer showing us their distillation license: they needed a 
license to run a still, even though it was only water.  In any event, I asked 
about how they knew they needed to replace the water and was told they they 
measured leakage current through the water. I was a very young ham at the time, 
the only one in the group, and asked most of the questions. 

Kim N5OP

"People that make music together cannot be enemies, at least as long as the 
music lasts." -- Paul Hindemith

> On Apr 14, 2018, at 23:02, Roger (K8RI) <> wrote:
> Having spent many years of my life (in another life. I left there in 87 and 
> went to college) working with induction heating from KHz to MHz and air 
> cooled 2 KW to 6KW water cooled into the hundreds of KW with generators that 
> ran days at a time with cooling water on 24 X 7 X 365.  Running 30 some 24 X 
> 7 12 KW (water cooled, not vapor phase) and a five hundred to a thousand 
> gallon reservoir.  We changed water twice a year. Water changes were usually 
> warranted when the generators started tripping out due to low resistivity. 
> Often, if not usually caused by a disgruntled, or curious, operator dumping 
> one of these little packs of salt you get at restaurants, into the system. 
> Bodily fluids expelled into one of the open drains were more efficient or at 
> least as quick as the salt. Sometimes happened on a bet too! So coolant life 
> "can be" quite long, but is typically based on the total liquid compared to 
> the metal in the system and the coolant temp.  I seriously doubt you will 
> have t
 o worry about someone relieving themselves into the boiler, which could be 
considered hazardous to the reliever's health, or at least important body parts.
> Copper held up well. Brass fittings? ahhh...not quite so well. 1/2" brass 
> hose-barbs would take on a reddish brown color and could be crushed with 
> finger pressure. We usually became aware it was getting time to change them 
> after one failed.  60 psi in a half inch hose, can dump a lot of water into a 
> 6 KV @ 2A circuit and takes little time to recognize.  Noisy and expensive 
> too!:-D  As a SWAG I's say the brass lasted a couple years.
> Oh! At 6+ KVDC we used about 8 to 12' of hose for anode isolation.  We to 
> uses a solenoid coil form for the hose
> 73, Roger (K8RI)
>> On 4/13/2018 9:40 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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