Hi Steve,

The biggest reason to exchange the 811's for 572B's is that the 572's have
much more "head room."  This means you can move further from the frequency
on which you tuned up before having to retune your amp.  Otherwise, if the
811's are working for you, I agree.

Take care and very 73. 


 
Kevin :)
Amateur Radio:  K7RX
 

-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Steve Dresser
Sent: Monday, August 16, 2010 06:29
To: [log in to unmask]
Subject: Re: Kevin's amplifier tuning cheat sheet

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
>> >>
>> >>
>> >
>