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Re: [Amps] GS-35b fully-submersed oil cooling

Subject: Re: [Amps] GS-35b fully-submersed oil cooling
From: Steve Wright <>
Date: Sat, 21 Mar 2015 07:45:30 +1300
List-post: <">>

On 21/03/15 05:00,

"Jim Thomson"<>wrote:

  properly designed system would have a sump where the water would
naturally separate from the oil, and a valve to drain the small
amounts of water collected over time.

No. A properly designed system won't have a single pin-drop of moisture in it to begin with, and if it did, a refrigerant drier would remove it.

### The problem with oil immersion...which is used on some eimac tubes per the
Eimac catalog is..... if you install a metal tub surrounding the tube... you 
now have
stray C from the enclosure to the the anode....which can affect the PI net on 
upper bands.   RF parts used to sell a metal chimney..with a teflon ring on 
top, for
the 3CX-3000A7 tube..for air cooling.  It added 10 pf of C.
Tube is 24 pf from anode to grid, measured on a wooden bench.
And when inserted in the socket, rose to 33 pf.
That extra 9 pf is caused by the proximity of the lower anode fins to the 
chassis below.
Once the metal chimney was installed, it rose to 43 pf.

Thank you for that. I had a quick google, but did someone want to offer an opinion (or better) that such a metal chimney or (container/tub) might make a 6m amplifier infeasible?

The increased dielectric constant of the oil will also act to increase that capacitance.

If the Eimac thought it was appropriate to use a metal ring in close proximity, then likely it was usable for I to do it as well.

It also seems, there may be the opportunity to entirely and safely encapsulate the HT

##  any oil cooling scheme would involve the use of an external oil pump +  
external air
cooled radiator. ANY leaks anywhere, and you end up with a real mess on your 

Of course. But there are quality crimp fittings available everywhere. I'd also have a drip tray under the tube sockets. In the end, it's a nice clean-smelling quality oil. It isn't dog shit.


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