[Amps] Fan Noise in GS-35b Amplifiers

[Roger]

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 at aol.com" <mikflathead at aol.com>
> To: paul at n1bug.com; w9gt at frontier.com; amps at 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 at n1bug.com>
> To: Jack C. Shutt <w9gt at frontier.com>; amps <amps at 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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