[Amps] [BULK] - Re: SB200 loading problem

[carl seyersdahl]

I have been following this thread and have something to offer here.
   I can't think of why the loading problem , BUT, the hi voltage appears
too  low. Has it been measured with an external voltmeter?? It should be
about 2400 vdc no load and around 2100 fully loaded.!! I have always run the
200 at about 75 watts in , and using a pulser for tuning I generally got
about 750 watts PEP output on all bands except 15 - 10 m.on those bands it
was down to about 700 w. again PEP with a pulser.
    also , how much input power and what is the input swr??
   I use two Autek wm-1 meters , one in , one out, and altho I can't vouch
for their accuracy, I'd say they are well within the 5-10% range , all
things considered.!!!
     I have all the info here on the SB-200/201 if anyone should need it.
Have a good day my friends.
     carl / kz5ca
  P.S. I always have run that type amp on 120 ac input. , and remember that
the transformer was designed when the" standard "
  line voltage was closer to 110-115 , not what is is today, at my qth it is
generally closer to 120-125.!!!
 Need more info?? e-mail me.
  carl / kz5ca (not a genius , BUT)
----- Original Message ----- 
From: "Steve Thompson" <g8gsq at ic24.net>
To: "John Parkins" <john at g8kvp.com>
Cc: <amps at contesting.com>
Sent: Tuesday, September 20, 2005 5:02 AM
Subject: Re: [Amps] [BULK] - Re: SB200 loading problem


>
>
> John Parkins wrote:
> > Hello Steve,
> >
> > Tuesday, September 20, 2005, 9:19:04 AM, you wrote:
> >
> >
> > ST> You could see the same effect if the tank coil inductance is too
low -
> > ST> eg if part of it  was shorted out when it should be in circuit.
> >
> > ST> Max load cap. gives you a high anode load resistance. The circuit
might
> > ST> like this if the ht was higher than intended, but I can't see
runnning
> > ST> 240V into a 220V input, for example, making enough difference. Tired
> > ST> valves that don't have the emission to cope with a lower load
resistance
> > ST> might also do it.
> >
> > ST> What gain and output power are you getting, and how do they compare
with
> > ST> the spec. for the amp? Does the anode current dip - is the dip at
max rf
> > ST> output?
> >
> > ST> Steve
> >
> > I was wondering about the tank coil although I've not noticed a
> > problem with it visually, perhaps adding a turn or two??
>
> Can't see a problem with trying it as an experiment - I'd been thinking
> along the lines of whether part of the coil was left shorted by the
> bandswitch.
> >
> > The HT runs at 2100 off load and 1950 on load. As I've said in other
> > replies I have a spare set of valves and switching them around hasn't
> > helped.
>
> I don't know the amp, but from what I read that looks about right.
> >
> > Gain and output seems to be OK, although I've seen that some say they
> > get more output, on 80 & 40m 80w in gets around 625 - 650w out. As far
> > as the anode current, dip it is deepest at max rf out.
> >
> I forgot to ask - what's the anode current / efficiency?
>
> In the end, if it's all about right and output power and linearity are
> ok, then you could do worse than leave it alone. In your place I
> couldn't, but I spend much more time fiddling with equipment than
> actually using it!
>
> There's a good looking set of notes at mods.dk if you put in sb200 on
> the article search.
>
> Steve
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