Yep, it requires some machine tools to do it neatly. The 8072, 8121, and
8122, and a few variants, are the same basic tube.
The 8121 with vertical grooves machined in also do a good job in the
NCL-2000 and are becoming more available as equipment and spares are being
retired.
They are also a same socket swap and air flow compatible into a MLA-1250 and
2500 if you want to make the PS changes and swamped grid input as in the
NCL-2000.
Carl
KM1H
----- Original Message -----
From: "Jim W7RY" <w7ry@centurytel.net>
To: "Michael Clarson" <wv2zow@gmail.com>; "Fuqua, Bill L" <wlfuqu00@uky.edu>
Cc: <amps@contesting.com>
Sent: Friday, May 09, 2014 10:48 PM
Subject: [Amps] 8122 and 8072
Quite a while ago, I was tying to figure out how to get the cooler fins
off of an 8122 and back onto an 8072. It looks like they are welded onto
the outer plate structure of the 8122.
They are the same tube with the exact ratings (except for plate
dissipation).
73
Jim W7RY
-----Original Message-----
From: Michael Clarson
Sent: Friday, May 09, 2014 12:46 PM
To: Fuqua, Bill L
Cc: amps@contesting.com
Subject: Re: [Amps] Using computer CPU coolers on GI46b triode ?
Bill: Yes -- Familar with the 8072. It was used in a lot of land mobile
radios, conduction cooled. They would run at 100 Watts out. Plate
dissipation was only 100 Watts in the conduction cooled mode. To contrast
conduction vs forced air, the 8122, same tube with forced air heat sink
had
a 400 Watt dissipation. The 8072 was a deal in the late 1970s. One could
buy them new via conventional channels for $20. --Mike, WV2ZOW
On Fri, May 9, 2014 at 2:55 PM, Fuqua, Bill L <wlfuqu00@uky.edu> wrote:
I once made a heat sink for 4 6AG7 tubes by drilling out a large block
of aluminum boring
holes in it aprox. 1 in dia and using a tungsten tipped saw blade cut
slots for fins. Worked
well. Somewhere I have some heat sinks for some 8072's ( 8122 without
fins) used in
a 500 watt plasma generators. Some were made of sheet metal, and others
were machined
blocks, both were forced air cooled, neither worked very well. The
manufacturer had to
can the product. They were not reliable. At that time 8072's were much
cheaper than 8122s.
I would not recommend use of heat pipes like those used in many
computers. A computer has
to dissipate much less heat than a power tube.
73
Bill wa4lav
_______________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Joe Subich, W4TV [
lists@subich.com]
Sent: Friday, May 09, 2014 2:17 PM
To: amps@contesting.com
Subject: Re: [Amps] Using computer CPU coolers on GI46b triode ?
On 5/9/2014 11:12 AM, Carl wrote:
> Subject: Re: [Amps] Using computer CPU coolers on GI46b triode ?
>
> I can easily see boring a CPU sink as a simpler alternative as long as
> a
> round silicone rubber chimney isnt required.
That may be possible with an old "block with fins" type heat sink but
many of the newer ones use a relatively thin plate/heat spreader and
tubes filled with a heat transfer fluid. The tubes bend upward to a
radiator in the normal air flow or with or have a fan mounted to the
radiator. Drilling/boring one of those would damage the heat tubes
and render it useless.
73,
... Joe, W4TV
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