On 2/20/2014 9:59 AM, Jack C. Shutt wrote:
Yes, water cooling would be really neat! I understand that the GS-35a version
of the tube has
a water-jacket, but you never see those for sale. I have seen some home
brew examples for other
tubes, but it might be a little difficult to build my own water-jacket
and then.... how do you
provide a water tight seal around the tube that will withstand the heat?
With that tube you could silver solder the jacket at the top and botton
or put grooved rims for o-rings at top and bottom.
You still need a fan to cool the ceramic to metal seals.
I suppose a simple
fish tank pump and some plastic tubing would work for coolant
circulation and then maybe some sort
of small radiator or cooling tank to dissipate the heat. Seems like it
would work if the details
could be worked out.
It doesn't take a lot of flow, but I doubt a fish tank pump would have
enough volume for the tube to run the legal limit. 5psi on 1/4" tubing
should be sufficient, but I've not run the figures.IIRC that info may be
in "The Handbook".
Don't forget the hoses/tubes in and out have to be long enough to keep
the leakage current down. Typically both tubes are wound 3 or 4 turns on
a form 1.5 or 2" form (or what ever is handy, larger than 1.5". You need
little pressure so 1/4" Tygon tubing should be sufficient. Remember
that distilled and deionized water really like brass fittings so shut
the water off and let the system drain after cool down. With clear
Tygon you can see any crud build up.
In systems that ran 24 X 7 we rarely made more than a year or two with
brass hose barbs. I don't know which metal was dissolved, but the
fittings took on a dull copper color and could be crushed easily between
your thumb and forefinger. We usually discovered the problem when the
connector failed and the hose blew off. These were 1/2" with about 60
psi IIRC. IOW, a failure was usually spectacular and messy. I don't
remember any of them arcing though.
When I went started there we were moving into (I think) 3 main
buildings. now it's grown a bit (43-26-08N X 84-09-53W) bout 3/4 of a sq
mile. I don't even recognize anything...except the parking lot.
73
Roger (K8RI)
73, Jack, W9GT
________________________________
From: "mikflathead@aol.com" <mikflathead@aol.com>
To: paul@n1bug.com; w9gt@frontier.com; amps@contesting.com
Sent: Thursday, February 20, 2014 9:42 AM
Subject: Re: [Amps] Fan Noise in GS-35b Amplifiers
Some builders water cool these tubes. It that an option?
-----Original Message-----
From: N1BUG <paul@n1bug.com>
To: Jack C. Shutt <w9gt@frontier.com>; amps <amps@contesting.com>
Sent: Thu, Feb 20, 2014 9:27 am
Subject: Re: [Amps] Fan Noise in GS-35b Amplifiers
I don't know what the "recommended" blower is, but bear in mind slow
speed blowers can be much less noisy than high speed ones. They tend
to be physically larger, however. On some prior amps I used high
speed (2500-3000 RPM I think) blowers that were physically rather
small. They got the job done but were very noisy. On my current
generation 4CX1500B amps I use Dayton 2C647 blowers. They run at
1500 RPM, but move about the same amount of air by using a larger
squirrel cage. They are much quieter. I suspect even this amount of
noise would be objectionable to many people but those blowers are
far less noisy than the 4" fan in my rack mount server case that
houses the shack PC. Something has to be done about that fan! 73,
Paul N1BUG On 02/19/2014 11:07 AM, Jack C. Shutt wrote:
I have gathered from all the info that I have read on amps using
the GS-35b that a healthy air flow is necessary to keep these
tubes happy. Unfortunately, the 100 CFM squirrel cage blower
that is recommended for this purpose is quite noisy. Any
suggestions for an effective cooling arrangement that is quieter?
I thought about remotely locating the blower and using a hose
duct to the amp, but this is just not practical in my shack.
Suggestions? 73, Jack, W9GT
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