Re: [Amps] 572B - News?

["Carl" <km1h@jeremy.qozzy.com>]

The FL-2100's with 572B's did not have sufficient bias for Svetlana and even 
some Chinese tubes, the fix was easy.
OTOH those amps have a wacky neutralizaion circuit that is far from stable 
on all bands and can take out the bandswitch. Modifying for the old Heath 
Chippewa or Gonset GSB-201 circuit took care of that.
The SB-201 is not fully neutralized on 10/12 M with any brand of tube and a 
similar rework saves a lot of "smoke" issues.
Carl
KM1H



> Plus, if I recall, there was a service bulletin on the 2100 (not sure it 
> it applied to the Z variant) regarding the use of the Svetlana tubes.  The 
> amp needed a modification (probably to the parasitic suppression?) to use 
> that tube.
> Al
> AB2ZY
> ________________________________________
> From: Amps <amps-bounces@contesting.com> on behalf of Carl 
> <km1h@jeremy.qozzy.com>
> Sent: Friday, November 7, 2014 1:03 PM
> To: David Harmon; 'Marcelo Cabral'; amps@contesting.com
> Subject: Re: [Amps] 572B - News?
>
> The Svetlana works OK but has a smaller anode and less dissipation. They
> havent been made in several years now.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "David Harmon" <k6xyz@sbcglobal.net>
> To: "'Marcelo Cabral'" <py1kr.marcelo@gmail.com>; <amps@contesting.com>
> Sent: Friday, November 07, 2014 12:25 PM
> Subject: Re: [Amps] 572B - News?
>
>
> > Marcelo.....
> > Try to find some 572-B made by Svetlana.......they are much better
> > quality.
> > I have had several sets of them and I prefer them over the Chinese mfgd
> > tubes.
> >
> >
> > 73
> >
> > David Harmon
> > K6XYZ
> > Sperry, OK
> >
> > -----Original Message-----
> > From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Marcelo
> > Cabral
> > Sent: Friday, November 7, 2014 11:18 AM
> > To: amps@contesting.com
> > Subject: Re: [Amps] 572B - News?
> >
> > Hi, Carl!
> >
> > Good news at the end!
> > Sincerely, I will try a MP pair of these new tubes after January, but I
> > haven't big expectations about their reliability.
> > But, if them survive at least one year, I must be finished the others
> > projects and be able for start this mod for GI7B. For today, I'll buy 
> > some
> > GI7B's from UR4LL, must be useful in a near future.
> > Thanks everyone, hope to meet everybody in CQWW CW soon.
> >
> > Marcelo - PY1KR
> >
> > -----Original Message-----
> > From: Carl [mailto:km1h@jeremy.qozzy.com]
> > Sent: sexta-feira, 7 de novembro de 2014 14:52
> > To: Marcelo Cabral; amps@contesting.com
> > Subject: Re: [Amps] 572B - News?
> >
> > RF Parts will be taking new 572B orders in Jan 2015, Id rather wait than
> > hack up a perfectly good amp for an inferior tube.
> > http://www.rfparts.com/tubes/tubes-572b.html
> >
> > Carl
> > KM1H
> >
> >
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