Re: [Amps] re cooling of coils

["Ian White, G3SEK" <G3SEK@ifwtech.co.uk>]

W0UN -- John Brosnahan wrote:
> > I don't know what type of fan they supply, but low-noise Muffin-type 
> > fans are available that are at least 10dB quieter than the regular type.
>
>
> RE: QUIET MUFFIN FANS
>
> Ian--
>
> Couldn't agree more with what you say with one exception.  The optional muffin
> fan that was available from ETO for the Alpha 87A (and other models) during
> most of the 1990s WAS a very noisy fan.  And many hams opted to install
> a locally obtained, flea-market fan.  These were either noisy if they moved
> a lot of air or very quiet but ineffective at moving any air into 
> back-pressure.
>
> When I took over as president I went on a quest to find the ultimate muffin
> fan that moved a lot of air, worked reasonably well into back-pressure,
> and was as quiet as possible.  I found ONE fan that met my needs and
> in fact it was about 10dB or more quieter.  And this is the fan that was
> supplied by Alpha from about 1999 on.  Although I cannot speak for Alpha
> amplifiers now that the company is owned by Crosslink, I assume that they
> have continued to supply this "good" fan.
>
> This fan was chosen to provide good, turbulent air flow around the transformer
> as well as to reduce the actual exhaust air temperature, providing 
> increased cooling
> for the expensive 3CX800A7s.  During heavy contesting I have noted typically
> 10 or more degrees (F) reduction in air temp out the tube chimneys--as measure
> outside the amp but directly in the air path.
>
> The fan I chose was the Pabst 4580Z and it provided a great improvement for
> ambient noise in the shack.  To the point where some of my computers made
> more noise than the amp.  But that is another story.
>
> I highly recommend the Pabst 4580Z muffin fan.  Typically NOT something
> you will find at a flea market sale--but well worth the price of a new one.
> I believe Newark (in the US) still stocks them.

Papst certainly has a range of "low noise" and "super low noise" fans, 
and numbers of other manufacturers supply near-equivalents.

However, the quieter models also have a lower air flow rate, and it's 
vital to avoid installing a fan that has a lower flow rate than the main 
blower - the fan would then be choking the airflow instead of boosting 
it.

At least Alpha owners now know exactly which one to pick.

At a flea market, the quieter fans are generally recognisable by having 
blades with curved edges and rounded-off corners, but I've no idea how 
to tell "quiet" from "super quiet" without a catalog.


--
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
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