Unless you have air leaking in from other sources, all the air has to come
through the anode - so the amount of cold air getting to the lower anode and
filament/ceramic seal will be the same amount as the heated air coming
through the top of the anode!
The problem is undoubtedly with the centrifugal blower which operates better
against a back pressure (pressurized chassis configuration) then trying to
pull negative pressure by sucking a vacuum from the top of the tube.
IMHO.
Al - K8EUR
----- Original Message -----
From: "ROBERT MARSTON" <rmarston@sbcglobal.net>
To: "Mark Beckwith" <mark@concertart.com>
Cc: <amps@contesting.com>
Sent: Saturday, February 14, 2004 11:27 AM
Subject: Re: [Amps] tube cooling
> Mark the critical points that need to be met when cooling a tube is to
keep both the plate and cathode-heater seals below their maximum ratings.
Typically they are between 200 and 250 Degrees Celsius. Sucking air from the
top of the anode in most cases does not provide sufficient airflow over the
cathode connections to keep them below their ratings. The water cooled
variant of the 4CX10K requires 30 CFM to keep the cathode seals below their
rating. You can get around this problem directing a second source of forced
air at the base. For all of the extra trouble this entails it's more
practcal to push the main source of cooling air up through the base in the
first place.
>
> Adios
>
> Bob K1TA
>
> Mark Beckwith <mark@concertart.com> wrote:
> Could you wise old sages help me with simple question - I seem to recall
> hearing that forced air cooling was not the same as, shall we say, sucked
> air cooling. Do I remember right? Seems you could destroy your amp if you
> tried to suck the air through the tube(s) tops as opposed to pushing it
> through from the bottoms.
>
> Advice please. Thanks in advance.
>
> Mark, N5OT
>
>
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