The tantalum plate Eimacs do a large amount of heat dissipation thru the
glass while the Chinese and Amperex graphite anodes heat up the anode pin.
This may be a reason that Eimac first introduced a graphite 3-500Z and then
quickly dropped it.
Ive suggested for years that SB-220 owners go with the high speed fan when
switching to graphite. Then they complain about the air noise; you cant
please some people!
Carl
KM1H
----- Original Message -----
From: Patrick Barthelow
To: km1h@jeremy.mv.com ; sub1@rogerhalstead.com ; amps@contesting.com
Sent: Thursday, July 01, 2010 11:18 PM
Subject: RE: [Amps] New High Efficiency 3-500Z plate caps
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
Arecibo Video Tours:
http://www.youtube.com/watch?v=vicxDnn6LEY
http://www.youtube.com/watch?v=7rFeXsVz8hE&NR=1
"The most exciting phrase to hear in Science, the one that heralds
new discoveries, is not "Eureka, I have found it!" but:
"That's funny..." ----Isaac Asimov
> 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
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
Hotmail has tools for the New Busy. Search, chat and e-mail from your inbox.
Learn more.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|