My Drake L-4B has straight sided Chimneys. I have also used very similar
Coleman lantern envelopes on home brew 3-500Z amps. The thru glass electrode
looks quite thick and substantial, same for the 3-1000Z, so, it is my guess it
plays a significant role in conduction of heat away from the anode. In
addition to radiative dissapation. The old Eimac app notes, or perhaps the
"Eimac Care and Feeding of Power tubes" used to have a drawing of the supposed
air flow beside and over the top of the tube, even if the chimney was only a
vertical cylinder. Showed the air going vertical between the chimney wall, and
the OD of the tube envelope then curving, allegedly following the curved top
contour to the anode, and anode cooler, and mentioned that cooling was afforded
there, even though the air was not mechanically forced inward. who knows..
The Eimac 3-500Zs of my Drake L-4B are originals, with late 60's date codes...
Best Regards,
73, de Pat Barthelow AA6EG
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> From: km1h@jeremy.mv.com
> To: sub1@rogerhalstead.com; amps@contesting.com
> Date: Thu, 1 Jul 2010 20:00:03 -0400
> Subject: Re: [Amps] New High Efficiency 3-500Z plate caps
>
>
>
> >
> >
> > On 7/1/2010 3:43 PM, John E. Cleeve wrote:
> >> Gentlemen,
> >>
> >>
> >>
> >> I cannot get to my stock of Eimac 3-500 glass chimneys at present, but I
> >> recall, the Eimac drawing of the 3-500 glass chimney shows that the top
> >> edge
> >> of the chimney is formed into a pronounced inward lip of about a quarter
> >> of
> >> an inch, or more,
> > IIRC the ones that were in my 2K4 were notably more.
> >> in width, which directs the emerging air flow coming up
> >> the chimney from around the side of the tube, over and across the top of
> >> the
> >> 3-500 and directed so as to cool the glass/metal seal of the anode cap
> >> connection. The "finned" top cap was, or still is, the one shown in most
> >> published designs for 3-500 amplifiers....73,
> > It may be, but it's in an area of null horizontal flow and the directed
> > air is coming in from all sides where it is deflected upwards.
> > Also the heat conducted to the Aluminum is limited by the material and
> > size of the plate conductor that exits through the glass.
> >
> > As some one has already mentioned, the sole purpose of the Aluminum
> > radiator is to help keep the seal temperature down.
> >
> > 73
> >
> > Roger (K8RI)
> >> John G3JVC / GM3JVC.
>
>
> The Eimac SK-406 chimney is indeed curved inward at the top; the aftermarket
> version used on many commercial amps is straight sided. This probably leads
> to confusion among those who arent familiar with both versions.
>
> Carl
> KM1H
>
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