[Amps] Fan Noise in GS-35b Amplifiers

[Roger (K8RI)]

On 2/20/2014 10:22 AM, TexasRF at aol.com wrote:
> Jack, many homebrewers hang the blower off the rear panel to allow
> pressurizing the entire amplifier cabinet. That certainly gets the cooling job
> done but with maximum blower noise.
>
> Another approach is to locate the blower inside the amplifier and only
> pressurize the tube from the bottom. Ameritron AL1200,1500 and maybe others
> work  that way and have much lower blower noise.
>

The smaller Alphas went that route as well.
My 76A has a muffin fan on the back, blowing into the cabinet ans a 
squirrel cage blower in the middle, pressurizing the tube base 
compartment and silicone rubber chimneys to the top from the tubes.

73

Roger (K8RI)

> My homebrew vhf and uhf amplifiers are built that way. There is a three or
> four inch diameter hole in the rear panel for air intake. The hole is
> covered  with a K&S round air filter to keep dust and bugs out. The filter
> further  reduces the noise and keeps the amplifier clean as a whistle inside.
>
> 73,
> Gerald K5GW
>
>
>
>
> In a message dated 2/20/2014 6:51:43 A.M. Pacific Standard Time,
> w9gt at frontier.com writes:
>
> Yes,  that Dayton blower is a good one to use, however, it is still quite
> loud even  with the slower speed.  Of course, you can reduce the fan speed on
>   receive, but when transmitting, the noise is objectionable.  I'm
> wondering if slower speed and higher volume really translates to adequate  cooling
> if the actual air pressure is not there.  Many blowers will  provide what
> seems to be adequate air flow, but with back pressure, just don't  provide
> sufficient flow.  I have seen several European hams' GS-35b amps  with what look
> like just "muffin" type fans.  Those things are pretty  loud anyway and I
> don't think they move enough air.  I have seen  examples, also where they are
> using two "muffin" type fans.....one above the  anode cooler pulling air
> out of the enclosure and one below the chassis  blowing upward thru the tube.
> There has to be some of you folks out  there who have a "quieter" solution??
> 73,  Jack,  W9GT
>
>
> ________________________________
> From: N1BUG  <paul at n1bug.com>
> To: Jack C. Shutt <w9gt at frontier.com>;  "amps at contesting.com"
> <amps at 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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