Dont overlook a good muffin fan either. The EBM Papst 4600N was used in
later production LK-800's using the 3 3CPX800A7's at about 3100V. That is a
lot of fin area and back pressure.
They are also fine to run at reduced voltage in receive or low duty cycle.
Carl
KM1H
----- Original Message -----
From: "N1BUG" <paul@n1bug.com>
To: "Jack C. Shutt" <w9gt@frontier.com>; <amps@contesting.com>
Sent: Thursday, February 20, 2014 9:26 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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