Agreed Steve - just my thoughts that changing tubes is something we
can competently do. Another thought I had - pay really close
attention to how a something looks before you start working on
it!! If I understand something closed and carefully open it I stand
a good chance of re-closing it!!! maaybe that is obvious but I have
carelessly taken things apart and then had a hell of a battle getting
them back together!! Not long ago the flushing mechanism on one of
our toilets fell apart. I spent a really long time trying to figure
it out and I lost!! Called our oldest son and he came by and had the
job done in two minutes!!! And now that it is the way it is supposed
to be and I understand it, I'll be able to fix it myself the next
time!! (Probably)!!
Thanks.
Pat, K9JAUAt 08:28 AM 8/16/2010, you wrote:
>Pat,
>
>I've changed many a tube, but I don't see any reason to do so while the 811s
>are still working.
>
>Steve
>
>----- Original Message -----
>From: "Pat Byrne" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Sunday, August 15, 2010 22:16
>Subject: Re: Kevin's amplifier tuning cheat sheet
>
>
> > In the old days!! when we had tubes to change it was never a
> > problem. Occasionally tubes had to be neutralized - that was
> > something that as a blind man I couldn't do. It involved watching
> > grid current and making adjustments to stop that current from
> > showing. Only a problem with triodes and no longer an applicable concern.
> > Not to demean anyone's knowledge or abilities but the tubes will only
> > go in the "right" way and the plate cap just presses on to the top of the
> > tube.
> > Hope this helps.
> > Pat, K9JAu At 08:48 PM 8/15/2010, you wrote:
> >>Tom,
> >>
> >>You don't need an additional meter--the ones you need to read are already
> >>on
> >>the amplifier. I don't think I'm quite ready to change the tubes,
> >>especially for a $200 price, although I'll probably do so if I have to
> >>replace them.
> >>
> >>Steve
> >>
> >>----- Original Message -----
> >>From: "tom behler" <[log in to unmask]>
> >>To: <[log in to unmask]>
> >>Sent: Sunday, August 15, 2010 21:21
> >>Subject: Re: Kevin's amplifier tuning cheat sheet
> >>
> >>
> >> > Steve:
> >> >
> >> >
> >> > Well, so far, your experiences come pretty close to mine.
> >> >
> >> > Like you, I want to get someone sighted over here sometime with a
> >> > meter,
> >> > and
> >> > a familiarity with the amp and its characteristics, so I can determine
> >> > how
> >> > I'm actually doing.
> >> >
> >> > All of this adds up to why I bought the 572B's.
> >> >
> >> > I figured that with more robust tubes, I at least have less of a chance
> >> > for
> >> > all heck to break loose if I happen to make a blunder in the tuning
> >> > process.
> >> >
> >> > 73 from Tom Behler: KB8TYJ
> >> >
> >> > ----- Original Message -----
> >> > From: "Steve Dresser" <[log in to unmask]>
> >> > To: "tom behler" <[log in to unmask]>
> >> > Sent: Sunday, August 15, 2010 8:34 PM
> >> > Subject: Re: Kevin's amplifier tuning cheat sheet
> >> >
> >> >
> >> > Tom,
> >> >
> >> > Since this is my first tube amplifier, I attribute my success more to
> >> > luck
> >> > than experience. Nevertheless, a few things seem clear to me:
> >> >
> >> > First, as long as you try to run the amplifier within specified limits,
> >> > you
> >> > probably won't get into trouble. For that reason, I avoid driving it
> >> > with
> >> > more than 70 watts of continuous carrier.
> >> >
> >> > Second, things break down in a hurry if the plate current is high.
> >> > Therefore, I adjust the plate current so the amplifier is putting out
> >> > maximum power, which means the output circuit is in resonance, which
> >> > means
> >> > the plate current is at minimum.
> >> >
> >> > Finally, I worry about the grid current which, from what I understand,
> >> > should be high enough to keep the finals biased properly, which means
> >> > that
> >> > I
> >> > adjust it to the point where the output power begins to decrease.
> >> >
> >> > Thus far, I haven't blown anything up, and nobody has ever reported
> >> > that
> >> > my
> >> > signal is non-linear, which I hope means that I'm operating things
> >> > pretty
> >> > close to where they should be. One of these days, I'll be lucky enough
> >> > to
> >> > have someone sighted around to read the meters and see how close I
> >> > really
> >> > am. Meanwhile, I'll just be alert for smoke, and hope I don't smell
> >> > any.
> >> >
> >> > Steve
> >> >
> >> > ----- Original Message -----
> >> > From: "tom behler" <[log in to unmask]>
> >> > To: "Steve Dresser" <[log in to unmask]>
> >> > Sent: Sunday, August 15, 2010 19:59
> >> > Subject: Re: Kevin's amplifier tuning cheat sheet
> >> >
> >> >
> >> >> Well, Steve, you are much more experienced than I am with these
> >> >> things,
> >> >> and my thought at this point would be: "If your strategy works, don't
> >> >> change it.".
> >> >>
> >> >> I have to admit that I still get a bit apprehensive when doing the
> >> >> tuning
> >> >> procedure, but I just take my time, and work through each step, giving
> >> >> things periodic breaks in the process and, so far, so good.
> >> >>
> >> >> Tom Behler: KB8TYJ
> >> >> ----- Original Message -----
> >> >> From: "Steve Dresser" <[log in to unmask]>
> >> >> To: "tom behler" <[log in to unmask]>
> >> >> Sent: Sunday, August 15, 2010 5:51 PM
> >> >> Subject: Re: Kevin's amplifier tuning cheat sheet
> >> >>
> >> >>
> >> >> Thanks, Tom. I have considered connecting a VCO across the
> >> >> amplifier's
> >> >> meters so I could actually read the plate and grid current, but my
> >> >> "maximum
> >> >> smoke" method seems to work, and laziness prevails. Nevertheless,
> >> >> it's
> >> >> good
> >> >> to know the actual current info.
> >> >>
> >> >> Steve
> >> >>
> >> >>
> >> >
> >
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