[Amps] Svetlana 572B and FL-2100Z

[R.Measures]

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
>>
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>
>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org