[ARC5] 12 V Power pentode.

[Dennis Monticelli]

Gentlemen,

The video amp power pentodes have significant plate dissipation capability,
especially those designed for color TVs like 12HG7 and 12GN7.  They can
handle some serious power.  I know because I have built transmitters with
them.

The 12HG7 is 10W plate dissipation and the 12GN7 is 11.5W.   The 12BY7 at
6.5W is a relative lightweight.

Of all the octals mentioned in this thread only the 6F6 can claim to be in
the same league with its 11W plate rating.  However, it's plate current vs
grid voltage curves are significantly inferior.  The HG7 and the GN7 will
run rings around it in class C where peak cathode currents really matter.
I know this from experience not just IV curves.

If Ken's application is RF then there is the added advantage of plate to
grid isolation in favor of the TV tubes.

BTW, I have seen 12HG7s in larger diameter envelopes than the standard 9
pin bottle, giving the appearance of better heat shedding.

Dennis AE6C

On Sun, Apr 10, 2016 at 2:21 PM, Leslie Smith <vk2bcu at operamail.com> wrote:

>   Hello All,
>   The 1941 RCA handbook (May 1, 1942) lists the 12A6 as a "beam power
> amplifier"
>   I was surprised to see how many "beam" tubes were used, and how few
> "pentodes" (as distinct from 'beam' tubes) were used as power amplifiers.
> Even the 12AQ5 is a beam tube.
>
>   I don't know much about 'tubes' or the history of 'tubes' but it seems
> to me that the 12A6 (or 25A6) was the 'grandfather' of  the beam 'tubes'.
>
>
>    73 de Les Smith
>    vk2bcu at operamail.com
>
>
>
> On Mon, Apr 11, 2016, at 04:26, Dennis DuValll via ARC5 wrote:
>
>
>
> Ken,
>
> How about the 12A6?
>
> Dennis D.  W7QHO
> Glendale, CA
>
> ****************
>
>
>
>
>
>
> On Apr 10, 2016, at 6:03 AM, Phillip Carpenter <carpenterpa at tds.net>
> wrote:
>
> Ken,
>
> All I could come up with was the 12BY7 9 pin miniature and the 25A6 octal
> which has a 25 volt filament.
>
> Respectfully,
>
> Phillip
>
> Sent from my iPhone
>
>
> On Apr 9, 2016, at 11:47 PM, Kenneth G. Gordon <kgordon2006 at frontier.com>
> wrote:
>
> Does anyone here know of a power-pentode, which is 1) not a beam-tube, 2)
> has a 12.6 V filament, and 3) might have an octal base?
>
> #3 isn't all that important: I can build an adapter. But #s 1 and 2 are.
> And #1
> is of prime importance.
>
> I can't think of any.
>
> Anyone?
>
> Kenneth G. Gordon W7EKB
>
> "Courage is being scared to death but saddling up anyway."--- John   Wayne
>
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