[Amps] Fan Noise in GS-35b Amplifiers

[Roger]

On 2/20/2014 9:26 AM, N1BUG wrote:

Is it the blower that is noisy, or the air that is noisy?  On my 
4CX-1500B/FU728F the noise fron the exhaust is far louder than the fan 
and particularly in "high blower"

A comment on "off axis air flow from fans.  Most muffin type fans have 
an aerodynamic shroud. Mine on the amps and computers have very little 
flow beyond about 20 degrees off axis until you get several feet out.

Once past a couple feet, even a straight flow will spread rapidly due to 
turbulence between the flow and the steady room air.

73

Roger (K8RI)


> 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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