Pat,
I really hate it when I take something apart after carefully studying it,
and start to reassemble it only to realize that I'm not completely sure how
it looked before I took it apart. I would say it makes me tear out my hair,
but I have so little left.
Steve
----- Original Message -----
From: "Pat Byrne" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, August 16, 2010 18:35
Subject: Re: Kevin's amplifier tuning cheat sheet
> 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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