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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