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[Amps] Liquid cooling

To: amps@contesting.com
Subject: [Amps] Liquid cooling
From: Robert Briggs <vk3zl@bigpond.com>
Date: Tue, 06 Apr 2010 10:18:14 +1000
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Good to see more discussion re liquid cooling. However, aside from the 
merits of various cooling agents, water cooling is probably the simplest 
and most practical method for the average ham station....

I recently built and now have in full time ham CW use, a water cooled 
GS-35B, a pair of GI-7BT triodes in a new 40/20 meter duel band 
amplifier and I am just completing a 2 meter 2 x GI-7BT water cooled 
amplifier for the shack....Like most hams I have been running various 
air cooled home brew amplifiers using the general run of the mill glass 
tubes and ceramics...Noisy blowers, dust accumulation etc have always 
been the norm, along with the hit and miss guesses that the tubes are 
running within their seal limits etc..

I decided to have a go at water cooling some of the Russian triodes 
readily available and fairly cheap, and have removable anode air 
coolers....There was little practical information to be found on the 
internet so I went ahead and constructed two copper water manifolds for 
the GS-31 and 35B triodes using only imagination and what appeared to be 
a practical approach...My greatest worry was regarding the actual water 
system, hoses, pump, heat exchanger etc...

I was able to get excellent advice from two members from this reflector, 
many thanks to Roger and Tom.....The main points are to use vinyl hose 
for transporting the water to and from the tube from the reservoir, 
allowing for 1000volts per meter of hose....I am using small 12 volt 
1000LPH submersible pond pumps which give me 4 liters per minute of 
water flow through 1/2 inch hose...I am using small copper car heater 
radiators as a heat exchanger 6x6x2 inches with a near silent 240 volt 
muffin fan blowing air through the core....I wanted to keep all metal 
copper but the heat exchangers have brass tanks each end of the core...I 
have the heat exchanger grounded through a 0-1ma meter....My water 
reservoirs contain 12 liters of distilled water....Current leakage to 
ground is typically 200ua at room temperature rising to around 350-400ua 
at 40C....It takes a long CW session to warm the water past 30C with 
this system...

Now, my amplifiers are only run at a modest power output, however I am 
completely happy with  water cooling....I have no noisy blowers to 
contend with, the system is clean simple and as far as I am concerned 
safe....The only difference to running air cooled is the addition of the 
water hoses, out of sight like other cables and the water cooler under 
the operating bench...

Contrary to some beliefs these Russian tubes are excellent value and 
give good account for themselves...I have only been using them for 3 
years or so but have yet to have a failure....I guess one could quite 
easily build a water manifold for the Yc-156, 8877 etc if one wanted to 
and achieve results similar to my own experience....

Bottom line is, we are radio amateurs and with a little ingenuity we can 
achieve anything..Nothing beats building your own equipment, putting it 
on air and having the enjoyment of having done it yourself....

Bob..VK3ZL..


 


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