[Amps] Svetlana 572B and FL-2100Z

Peter Frenning, OZ1PIF oz1pif at privat.dk
Sat Aug 28 10:34:19 EDT 2004


Rich and Group,

I was never able to have the 2000B yield more than 300W with the 572Bs, with
the QB4/1100 (both grid and screen grounded) and 2900V an the plate it
easily gives 700+ on 80m and degrading to just under 500W on 10m, and, as
you say, it's much more stable - I would say rock-solid, and thus also much
easier to tune! With the Svetlanas it was well nigh impossible on the higher
bands!

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: "R. Measures" <r at somis.org>
To: "Peter Frenning, OZ1PIF" <oz1pif at privat.dk>
Cc: "Alek Petkovic" <vk6apk at eon.net.au>; <amps at contesting.com>
Sent: Saturday, August 28, 2004 4:26 PM
Subject: Re: [Amps] Svetlana 572B and FL-2100Z


>
> 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 at eon.net.au>
> > To: <amps at 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
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps at contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>
>




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