A few have asked me so here are some more details:
GRID: 0 @ rest, ~60 @ tx 40m
PLATE: 0 @ rest, ~285 @ tx 40m
HV: 2200 @ rest, 1850 @ tx 40m
On all bands, Grid and Plate are zero
at rest. Not sure if its the meter
or an indication of something more
serious...?
I tune for max output, measured with
an external meter (HM-102). The current
dip and max output don't coincide exactly,
but close. I can't get the plate current
anywhere near 500 mA.
At 7060 khz i get under 1.1:1 swr when i
use just my rig -> meter -> antenna.
When i measure the swr with the sb-200
in-line, i get just over 1.1:1 and still
over 120w forward. When i let the amp
kick in, i get a hair over 1.5:1 swr and
the power drops down to about 75w forward.
External meter then shows about 300w to
the antenna and a little over 1.5:1 swr.
Both tubes light up... maybe one is a hair
brighter than the other, but maybe its
just a smudge on my glasses. :)
Thanks for any assistance...
Steve, N9OH
--- carl seyresdahl <carlseye@tampabay.rr.com> wrote:
> Steve: how much hi voltage do you have. ?? With 300
> watts out it sounds like
> you might have one dead tube. How much grid current
> do you see?? should be
> less than half scale (100) ma. with two good tubes
> and proper loading. Run
> it with one tube removed and see what you get, then
> switch tubes and see
> what you get !!! If nothing else you can pinch hit
> with a pair of 811A's ,
> but don't hold the key down or you'll lose them .. !
> i've done that a few
> times for test purposes. the 811a isn't supposed to
> run at 2200 or so, but
> as i said, if you don't hold the key down for more
> than a few seconds
> they'll survive.
> the normal grid current for one tube is 50 ma..
> you might have some blown grid resistors also , so
> check those out. 33 ohms
> is the original value.
> Whatever You Do, Watch that hi-voltage, it'll
> rattle ur teeth and other
> more serious things, but then I hope you already
> know that !!!!
> I have the book on the 200 so if i can help let me
> know.!!!
> It would be thursday before I could copy any part
> of it but let me know
> what i can do for you!!!
> carl / kz5ca
> ----- Original Message -----
> From: "Steve Woodruff" <sjwoodr@yahoo.com>
> To: <amps@contesting.com>
> Sent: Monday, November 04, 2002 4:01 PM
> Subject: [Amps] troubleshooting a sb200
>
>
> > I'm getting lower than expected output from
> > a sb200 (abt 300w with 100w drive). Tubes
> > are 6-7, maybe 8 years old. Can someone point
> > me to a reference that has some steps that i
> > can take to determine the health of this amp?
> > Measurements to take and such like... I don't
> > have a tube tester, but if some feel that is
> > a probable fault area then i'll find someone
> > locally who does have one. Unfortunately i
> > do not have the original manual.
> >
> > Thanks,
> >
> > Steve, N9OH
> >
> >
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>
=====
----------------------------------------------------------
Steve Woodruff, N9OH @ 42.18N 88.34W, sjwoodr@yahoo.com
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