Yes I tried that Gerald, the internal tuner eases the SWR and improve drive,
still no luck beyond ~ 400 mA with 2 tubes on 20.
Regards /// Rahul
On Tue, Sep 8, 2009 at 10:51 PM, <TexasRF@aol.com> wrote:
> If you have a small antenna tuner, it can be used to reduce the vswr for
> test purposes.
>
> 73,
> Gerald K5GW
>
>
>
>
> In a message dated 9/8/2009 11:59:00 A.M. Central Daylight Time,
> vu3raz@gmail.com writes:
>
> I will try that tomorrow don. For the input circuit does nothing on 14 MHz
> VSWR is nowhere near 2.
>
> I am thinking of ripping the input tuned circuit and replacing it with a
> simple parallel resonant ckt as in the eimac design.
>
> Rahul
>
>
> On Tue, Sep 8, 2009 at 9:59 PM, Paul Playford <paul@w8aef.com> wrote:
>
> > Richard Measures, AG6K, has done a lot of work on SB-220s and talks about
> > the input circuit at:
> >
> > http://www.somis.org/SB220ci.html
> >
> > FWIW, Richard has his detractors however I have applied his modifications
> > to several SB-220s and a Henry 2K with great success.
> >
> > de Paul, W8AEF
> >
> > ZF2JI/ZF2TA FO8DX/FO8PLA 8Q7AA XZ0A VU7RG TX5D
> >
> > ----- Original Message ----- From: "Rahul Sathe" <vu3raz@gmail.com>
> > To: <amps@contesting.com>
> > Sent: Tuesday, September 08, 2009 8:32 AM
> > Subject: [Amps] SB221 Low Power Help
> >
> >
> >
> > Hello Experts,
> >>
> >> My name is Rahul call VU3RAZ. This is my first post to the list. I am
> >> seeking help on fixing my old SB221.
> >>
> >> as such the amp works on all bands, no arc or parastatics, tuning and
> >> loading is smooth and easy.. I am not able to load the amp to full rated
> >> plate current even with a 100 W drive with my 756 Pro3. Input VSWR is
> >> high,
> >> I tried tuning the input tuned circuit but no luck on few bands (20,
> 15).
> >> With the 756 ATU the things improve but I can not get plate current
> beyond
> >> ~
> >> 400 mA. Even tried disconnecting HT from each tube to see if one if the
> >> 3-500 is dead... both work but even with single tube I am not able to
> load
> >> the amp fully. Am I looking at dead (weak) tubes ... can both of them
> show
> >> exact same behavior? Or I am missing something I am not sure if I need
> to
> >> re
> >> build the PSU (replace caps)
> >>
> >> Please help...
> >>
> >> 73
> >> DE VU3RAZ
> >>
> >>
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