On Aug 28, 2004, at 6:26 AM, Peter Frenning, OZ1PIF wrote:
Alek and Group,
There are at least two diverging opinions on that! In some amps like
the
SB200 they are reportedly behaving quite well, wereas they are quite a
handfull in the FL2x00 series of amps, and possibly also in others. My
experience is with the FL2000B and that cost me two sets of tubes!
before I
finally gave up and rebuilt the amp using a single QB4/1100 (full
story on
my homepage)
A QB4 has less feedback C than a pair of 572Bs, so it is inherently
more stable. However, 572Bs can be tamed if one does his/her homework
and does not mind losing 2% or so of P-out on 10m.
cheers, Peter
Vy 73 de OZ1PIF, Peter
********** OZ1PIF **************
email: oz1pif(no-spam-filler)@privat.dk
http://home24.inet.tele.dk/oz1pif/
Ph. +45 4619 3239
Snailmail:
Peter Frenning
Ternevej 23
DK-4130 Viby Sj.
Denmark
***********************************
----- Original Message -----
From: "Alek Petkovic" <vk6apk@eon.net.au>
To: <amps@contesting.com>
Sent: Saturday, August 28, 2004 2:46 PM
Subject: [Amps] Svetlana 572B and FL-2100Z
A friend of mine Has recently bought a FL-2100Z and it is fitted with
Svetlana 572B tubes.
He has had a couple of bangs so far on 20m resulting in the loss of
the 22
Ohm parasitic suppressor resistors.
Also, a previous owner has put 33 Ohm wire wound resistors in the grid
circuit. The originals were of course non inductive resistors which
are
very hard to source here in Australia.
I am sending him some new 33 Ohm resistors and some nichrome wire to
make
up some new suppressors plus a glitch resistor.
I am also sending him some new Cetron tubes and have advised him to
get
rid
of the Svetlanas and put some extra resistance in the filament line to
reduce the voltage to a safer value.
Has anybody had any experience with Svetlana 572B tubes? I was under
the
impression that they spelled trouble in hf amplifiers. Is this a fact?
73, Alek
vk6APK
http://www.qrz.com/vk6apk
http://profiles.yahoo.com/vk6apk
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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