[Amps] 4-400A Plate

[Bill Fuqua]

The first glowing plate amplifier I made was using a pair of
250th's.  I drove them with a pair of 6146B and had about
2Kv on the plate.  Naturally I had to provide bias to the tube
even though it was cathode driven.  When I tuned up the plates
not only glowed red you could see the dark shadow of the
grid on them.
         I was only a young ham then and did not know that
you "can't  run 250th in grounded grid".  But it worked just
fine and I did get about 1KW plate input power to the
amp. Which meet those days 200 watts plate input to the
6146B's and 800 watts plate input to the 250th amp.
         Legal limit was 1000 watts DC plate input power
of all stages contributing power to the antenna. So I had to
include the driver.
         I mostly worked CW and some SSB then (in the 60's).
Now I wish I still had the hallicrafters HT-4 that I destroyed to make
the amplifier.

73
Bill wa4lav


At 06:12 AM 11/8/2002 -0800, Rich wrote:


> >!00 watts drive seems to be quite a lot for a single 4-400A G-G amp.
> >However, in some amplifiers I have noticed that the plate seems to
> >get hotter with some drive and cooler with even more drive.
> >This may be due to changes in efficiency as the drive is increased and
> >the tube is going from class A up toward  class B operation.
> >
> >Good luck.
> >I like to use the 4-250A instead of the 4-400A because they have the
> >same electrical characteristics but the 250s glow brighter.
> >
>**  Indeed, and it produces the same peak-emission as a 3-400, 3-500 and
>4-400.  Another good light show can be produced by the 8281/4cx15,000A.
>When a clear plastic chimney is used, electrons striking the alumina
>anode insulator below the anode-cooler, cause it to glow blue.
>
>cheers, Bill\
> >
> >At 03:12 AM 11/8/2002 -0800, Bill Smith wrote:
> >>I have installed a single 4-400A in my Swan Mark 1 for
> >>testing.  I am running it Zero Bias and Grounded
> >>Grid(it's being used as a triode).  It has 2500vdc
> >>plate voltage and a max of about 400ma with 100 watts
> >>of drive.  I am curious as to others experiences doing
> >>this with the 4-400A.  The plate gets red in SSB and
> >>CW with 100 watts of drive as I expected it should.  I
> >>back the drive down but even in SSB the plate still
> >>gets red.
> >>
> >>73,
> >>Bill
> >>
> >>Resting current is about 40ma.  I tested it with about
> >>100 watts of drive
> >>
> >>=====
> >>Bill Smith KO4NR
> >>
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>
>-  Rich..., 805.386.3734, www.vcnet.com/measures.
>
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