[Amps] cooling chimney?

[Pat Barthelow]

Regarding the cooling of the plate cap,  Eimac in their Applications notes show how, even though the Coleman
Pyrex cylinders have no curve, that the air, as it encounters the top of the tube,  curves anyway, and becomes a little turbulent, which I think is a good thing, as it encounters the glass curve leading to the plate cooler.  As I recall, the Drake L-4B  with 3-500Zs uses straight sided glass chimneys.  Their Plate Cooler, is distinctively different than the classic horizontal fins.  But the L-4 B is a well respected early amp design.  I have one, but it is in storage right now, so I cant double check to see if the chimneys are straight sided.   The 3-500Zs in it have had heavy use, for its whole life, and are the originals  are still installed with a 1968 Date Code.
The other excellent robust enhancement for cooling, is a Muffin Cooling fan sucking air from the outside of the cabinet just above the tubes.

Best, 
Pat, AA6EG

> From: bmaser at tampabay.rr.com
> To: km1h at jeremy.mv.com; hrd998cc at yahoo.com; kc0nxm at sbcglobal.net; amps at contesting.com
> Date: Mon, 14 Jul 2008 16:22:03 -0400
> Subject: Re: [Amps] cooling chimney?
> 
> I have always been told that the most important characteristic of cooling 
> glass tubes is that you have to cool the part of the plate cap where it 
> enters the top of the glass envelope.  Overheating at that place can cause 
> catastrophic failure.  I would be wary about using a Coleman lantern globe 
> because of this.  Besides, why not just go out and buy the correct chimney 
> that has been designed for the tube.  You wouldn't put recaps on a Porsche 
> Carrera.
> 
> Bob W6TR
> ----- Original Message ----- 
> From: "Carl" <km1h at jeremy.mv.com>
> To: <hrd998cc at yahoo.com>; "Stirling Schmidt" <kc0nxm at sbcglobal.net>; "AMPS 
> submit" <amps at contesting.com>
> Sent: Monday, July 14, 2008 4:04 PM
> Subject: Re: [Amps] cooling chimney?
> 
> 
> > This goes back to the 60's so I have no idea what is relevant today nor 
> > what
> > country those parts are made in now.
> >
> > Id suggest doing a Google and see whats current in discussions.
> >
> > And a call to Eimac should also generate an answer.
> >
> > Carl
> > KM1H
> >
> >
> > ----- Original Message ----- 
> > From: "Russ Williams" <hrd998cc at yahoo.com>
> > To: "Stirling Schmidt" <kc0nxm at sbcglobal.net>; "AMPS submit"
> > <amps at contesting.com>; "Carl" <km1h at jeremy.mv.com>
> > Sent: Monday, July 14, 2008 3:25 PM
> > Subject: Re: [Amps] cooling chimney?
> >
> >
> >> Carl, can you elaborate on the problems using Coleman chimneys?  I plan 
> >> on
> >> using them for a 4-400a project and also know of 2 other hams using them
> >> in conjunction with GS-35b's.  It seems the Pyrex/borosilicate glass 
> >> would
> >> be ideal for this application.  If there have been confirmed disasters
> >> using them, other avenues may need to be pursued.
> >>
> >> I suppose a test in the microwave oven would illuminate any faults in the
> >> Coleman's glass formula...
> >>
> >> Thanks.
> >>
> >> Russ W6OHM
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
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