[Amps] cooling tubes

[Gary Schafer]

There are muffin fans and there are muffin fans. Some are capable of working
under a fair amount of back pressure and some are not. You need to look at
the specs on the particular fan used.

73
Gary  K4FMX

> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Gudguyham at aol.com
> Sent: Tuesday, February 06, 2007 1:25 PM
> To: amps at contesting.com
> Subject: [Amps] cooling tubes
> 
> Nice thread on the vapor cooled Eimac tube, but  I have an experience  I'd
> like to share and see if anyone can comment.  Some time ago I had
> occasion to
> work on an Alpha 374 amp.  This amp has a pair of 3CX400's  (8874's)  That
> is a
> total plate dissipation of 800 watts similar to a  single 3CX800.  Anyway,
> this Alpha 374 cools these 2 tubes  by  pressurizing the entire RF
> compartment
> with a large muffin fan, the only air  escape is through a hole in the
> small
> chassis that the tubes are installed on  and then up through the tubes and
> out
> the top of the cabinet.  This amp  does not use a blower per se.  The
> question
> is could a muffin fan cool a  single 3CX800 tube "if" the fan was mounted
> right under a chassis that housed  the tube socket and then the only means
> of
> escape for the air was up through the  fins of the tube?  I understand the
> concept
> of air flow and that a back  pressure is a factor, but in this Alpha amp
> it
> seems to work.   Lou
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