I cannot think of a single reason, that means zero reasons, to build with a
572b. The GI7B is a far far far far far superior tube
(did I say far superior? hi hi) than the 572b. And all the rest of the amp is
essentially the same. 1 GI7B = 2 572b from a power
standpoint.
You can buy GI7BT at a reasonable price from QRO-STUFF.COM. They will ship
from a TX warehouse but the freight term is a bit odd.
The way it works is you get the delivery from TX, but you pay for a partial
shipment cost for the original transit from Russia -
which is why the freight cost seems so high.
2500V is the sweet-spot for B+ on that tube as well. A pair of them well
ventilated will run about 1KW out on the lower bands and
remain under the 700W plate dissipation limit for a pair. Match that with the
G3SEK triode control board and you will have a modern
amp.
Having said that, one thing to consider - it's often more expensive to build
unless you have a lot of time to hunt around for parts
on the cheap or unless you have a well stocked junkbox (most guys don't). And
to an extent, the same caviet applies to doing mods
on something like an SB200 - I beleive I must have the only $3000 SB200
upgraded amp on the planet! So if you are thinking you can
build for less than buying, you can get pretty far toward your goals with an
AL80 which is a much superior amp to an AL572 and uses
a much more rugged tube.
Good luck.
73, Jeff ACØC
www.ac0c.com
-----Original Message-----
From: Roger (K8RI)
Sent: Sunday, December 26, 2010 4:15 PM
To: amps@contesting.com
Subject: Re: [Amps] 572B AMP PLANS
On 12/26/2010 4:31 PM, JEREMY ENGBROCK wrote:
> I want to build an amp with 3 or 4 572b tubes. I would like to get 800 to
> 1000 watts output. I have a good high voltage supply
> for this project. Does anyone have any MODERN plans for an amp of this kind.
> I plan on running about 2500 volt under load on the
> anode if that will affect the tank values. Also does anyone know of a good US
> based source for GS35B OR GI7BT tubes.Thanks, 73
> Jeremy N0NZG
>
As Carl has already stated the AL-572 would make a good model for your
project.. It's a pretty basic circuit needing little in the way of
extra circuitry be it an old or "modern" design. They do have step
start and some other modern features to lower power drain in when not
transmitting and it includes ALC. You can download the information at
http://www.ameritron.com/Product.php?productid=AL-572 (data sheet
www.rfparts.com/pdf_docs/*572B*%20Svetlana.pdf ) AT 160 watts plate
dissipation each that is 640 watts total or 1067 watts of carrier out
in ICAS (amateur service). with 2900VDC at no load or 2500 full load on
the plates.
Ameritron would also be a good source for any parts no on hand or
difficult to find.
73 and good luck
Roger (K8RI)
>
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>
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